Host test plugin improvements, part 2: Copy plugins

# Description
This is second and last test suite modification related to reset / copy plugin architecture. Previous was done in https://github.com/mbedmicro/mbed/pull/597 pull request.

## Changes
* New copy / reset scheme introduced where plugins are implementing how to reset / flash mbed enabled device.
* Moved copy, reset and serial port management to host_test.
* added sew command line switched to pass e.g. test binary image location.
* Cleaned unnecessary host_test functionality (dead code).
* Refactored network tests to align with new reset / copy scheme.
 * Function test() and run() usage in host tests is now more unified - code is a bit more readable.
* Few tests and minor defects corrected on the way (test / test suite stability).

## Testing
I checked new functionality on our CI server with many MUTs:
(Some of the results below)
```
Test summary:
+---------+----------+-----------+-----------+---------------------------------------+--------------------+---------------+-------+
| Result  | Target   | Toolchain | Test ID   | Test Description                      | Elapsed Time (sec) | Timeout (sec) | Loops |
+---------+----------+-----------+-----------+---------------------------------------+--------------------+---------------+-------+
| OK      | LPC11U24 | uARM      | DTCT_1    | Simple detect test                    |        3.91        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | EXAMPLE_1 | /dev/null                             |        6.91        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_10   | Hello World                           |        3.74        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_11   | Ticker Int                            |       14.78        |       20      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_12   | C++                                   |        5.02        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_16   | RTC                                   |        7.93        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_2    | stdio                                 |        4.21        |       20      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_22   | Semihost                              |        4.1         |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_23   | Ticker Int us                         |       14.87        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_24   | Timeout Int us                        |       14.98        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_25   | Time us                               |       14.82        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_26   | Integer constant division             |        4.1         |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_34   | Ticker Two callbacks                  |        14.9        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_A1   | Basic                                 |        4.06        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_A2   | Semihost file system                  |        4.84        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_A21  | Call function before main (mbed_main) |        4.68        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | MBED_A9   | Serial Echo at 115200                 |        9.3         |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_1    | Basic thread                          |        15.0        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_2    | Mutex resource lock                   |       15.09        |       20      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_3    | Semaphore resource lock               |       12.03        |       20      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_4    | Signals messaging                     |        9.27        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_5    | Queue messaging                       |        5.94        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_6    | Mail messaging                        |        6.26        |       10      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_7    | Timer                                 |       15.06        |       15      |  1/1  |
| OK      | LPC11U24 | uARM      | RTOS_8    | ISR (Queue)                           |       10.05        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | DTCT_1    | Simple detect test                    |        4.26        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | EXAMPLE_1 | /dev/null                             |        7.32        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_10   | Hello World                           |        4.14        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_11   | Ticker Int                            |       15.17        |       20      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_12   | C++                                   |        5.32        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_16   | RTC                                   |        8.29        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_2    | stdio                                 |        4.52        |       20      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_22   | Semihost                              |        5.31        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_23   | Ticker Int us                         |       15.09        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_24   | Timeout Int us                        |       15.23        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_25   | Time us                               |       15.07        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_26   | Integer constant division             |        4.26        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_34   | Ticker Two callbacks                  |       15.04        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_A1   | Basic                                 |        4.23        |       10      |  1/1  |
| TIMEOUT | LPC1768  | ARM       | MBED_A18  | Interrupt vector relocation           |       20.84        |       10      |  0/1  |
| OK      | LPC1768  | ARM       | MBED_A2   | Semihost file system                  |        5.48        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_A21  | Call function before main (mbed_main) |        4.82        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | MBED_A9   | Serial Echo at 115200                 |        9.61        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_1    | Basic thread                          |       15.38        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_2    | Mutex resource lock                   |        14.5        |       20      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_3    | Semaphore resource lock               |        12.5        |       20      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_4    | Signals messaging                     |        9.44        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_5    | Queue messaging                       |        6.43        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_6    | Mail messaging                        |        6.52        |       10      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_7    | Timer                                 |       15.29        |       15      |  1/1  |
| OK      | LPC1768  | ARM       | RTOS_8    | ISR (Queue)                           |        9.42        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | DTCT_1    | Simple detect test                    |        4.09        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | EXAMPLE_1 | /dev/null                             |        6.97        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_10   | Hello World                           |        3.9         |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_11   | Ticker Int                            |       14.86        |       20      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_12   | C++                                   |        4.12        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_16   | RTC                                   |        7.93        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_2    | stdio                                 |        4.34        |       20      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_22   | Semihost                              |        4.13        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_23   | Ticker Int us                         |       14.77        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_24   | Timeout Int us                        |       14.84        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_25   | Time us                               |        14.7        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_26   | Integer constant division             |        4.04        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_34   | Ticker Two callbacks                  |       14.76        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_A1   | Basic                                 |        3.98        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_A18  | Interrupt vector relocation           |        9.19        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_A2   | Semihost file system                  |        5.06        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_A21  | Call function before main (mbed_main) |        4.21        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | MBED_A9   | Serial Echo at 115200                 |        9.33        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_1    | Basic thread                          |       14.81        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_2    | Mutex resource lock                   |       14.25        |       20      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_3    | Semaphore resource lock               |       12.13        |       20      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_4    | Signals messaging                     |        9.08        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_5    | Queue messaging                       |        6.1         |       10      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_6    | Mail messaging                        |        6.15        |       10      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_7    | Timer                                 |       14.78        |       15      |  1/1  |
| OK      | LPC1768  | uARM      | RTOS_8    | ISR (Queue)                           |        9.1         |       10      |  1/1  |
+---------+----------+-----------+-----------+---------------------------------------+--------------------+---------------+-------+
Result: 76 OK / 1 TIMEOUT

Completed in 716.10 sec
```

```
Test summary:
+--------+---------+-----------+-----------+---------------------------------------+--------------------+---------------+-------+
| Result | Target  | Toolchain | Test ID   | Test Description                      | Elapsed Time (sec) | Timeout (sec) | Loops |
+--------+---------+-----------+-----------+---------------------------------------+--------------------+---------------+-------+
| OK     | K64F    | ARM       | DTCT_1    | Simple detect test                    |        6.76        |       10      |  1/1  |
| OK     | K64F    | ARM       | EXAMPLE_1 | /dev/null                             |        9.81        |       10      |  1/1  |
| OK     | K64F    | ARM       | MBED_10   | Hello World                           |        6.6         |       10      |  1/1  |
| OK     | K64F    | ARM       | MBED_11   | Ticker Int                            |       16.68        |       20      |  1/1  |
| OK     | K64F    | ARM       | MBED_12   | C++                                   |        7.71        |       10      |  1/1  |
| OK     | K64F    | ARM       | MBED_16   | RTC                                   |       10.91        |       15      |  1/1  |
| OK     | K64F    | ARM       | MBED_2    | stdio                                 |        7.08        |       20      |  1/1  |
| OK     | K64F    | ARM       | MBED_23   | Ticker Int us                         |       16.62        |       15      |  1/1  |
| OK     | K64F    | ARM       | MBED_24   | Timeout Int us                        |       16.75        |       15      |  1/1  |
| OK     | K64F    | ARM       | MBED_25   | Time us                               |       16.59        |       15      |  1/1  |
| OK     | K64F    | ARM       | MBED_26   | Integer constant division             |        7.69        |       10      |  1/1  |
| OK     | K64F    | ARM       | MBED_34   | Ticker Two callbacks                  |        16.7        |       15      |  1/1  |
| OK     | K64F    | ARM       | MBED_A1   | Basic                                 |        7.63        |       10      |  1/1  |
| OK     | K64F    | ARM       | MBED_A21  | Call function before main (mbed_main) |        7.66        |       10      |  1/1  |
| OK     | K64F    | ARM       | MBED_A9   | Serial Echo at 115200                 |       12.14        |       10      |  1/1  |
| OK     | K64F    | ARM       | RTOS_1    | Basic thread                          |       18.18        |       15      |  1/1  |
| OK     | K64F    | ARM       | RTOS_2    | Mutex resource lock                   |       18.46        |       20      |  1/1  |
| OK     | K64F    | ARM       | RTOS_3    | Semaphore resource lock               |       15.44        |       20      |  1/1  |
| OK     | K64F    | ARM       | RTOS_4    | Signals messaging                     |       13.26        |       10      |  1/1  |
| OK     | K64F    | ARM       | RTOS_5    | Queue messaging                       |        9.33        |       10      |  1/1  |
| OK     | K64F    | ARM       | RTOS_6    | Mail messaging                        |        9.36        |       10      |  1/1  |
| OK     | K64F    | ARM       | RTOS_7    | Timer                                 |       18.12        |       15      |  1/1  |
| OK     | K64F    | ARM       | RTOS_8    | ISR (Queue)                           |       13.38        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | DTCT_1    | Simple detect test                    |        4.38        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | EXAMPLE_1 | /dev/null                             |        7.21        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_10   | Hello World                           |        4.34        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_11   | Ticker Int                            |       15.12        |       20      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_12   | C++                                   |        5.24        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_16   | RTC                                   |        8.28        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_2    | stdio                                 |        4.51        |       20      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_22   | Semihost                              |        5.29        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_23   | Ticker Int us                         |        15.1        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_24   | Timeout Int us                        |       15.19        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_25   | Time us                               |       15.06        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_26   | Integer constant division             |        5.23        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_34   | Ticker Two callbacks                  |       15.15        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_A1   | Basic                                 |        4.24        |       10      |  1/1  |
| FAIL   | LPC1768 | ARM       | MBED_A18  | Interrupt vector relocation           |        7.38        |       10      |  0/1  |
| OK     | LPC1768 | ARM       | MBED_A2   | Semihost file system                  |        5.49        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_A21  | Call function before main (mbed_main) |        4.21        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | MBED_A9   | Serial Echo at 115200                 |        9.55        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_1    | Basic thread                          |       15.46        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_2    | Mutex resource lock                   |       15.71        |       20      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_3    | Semaphore resource lock               |       12.53        |       20      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_4    | Signals messaging                     |        9.47        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_5    | Queue messaging                       |        6.49        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_6    | Mail messaging                        |        6.46        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_7    | Timer                                 |       15.26        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | RTOS_8    | ISR (Queue)                           |        9.59        |       10      |  1/1  |
+--------+---------+-----------+-----------+---------------------------------------+--------------------+---------------+-------+
Result: 1 FAIL / 48 OK

Completed in 528.25 sec
```

```
Test summary:
+--------+---------+-----------+---------+----------------------------+--------------------+---------------+-------+
| Result | Target  | Toolchain | Test ID | Test Description           | Elapsed Time (sec) | Timeout (sec) | Loops |
+--------+---------+-----------+---------+----------------------------+--------------------+---------------+-------+
| OK     | K64F    | ARM       | NET_1   | TCP client hello world     |        13.8        |       15      |  1/1  |
| OK     | K64F    | ARM       | NET_13  | TCP client echo loop       |       12.67        |       15      |  1/1  |
| OK     | K64F    | ARM       | NET_2   | NIST Internet Time Service |       14.93        |       15      |  1/1  |
| OK     | K64F    | ARM       | NET_3   | TCP echo server            |       11.98        |       10      |  1/1  |
| OK     | K64F    | ARM       | NET_4   | TCP echo client            |       12.08        |       10      |  1/1  |
| OK     | K64F    | ARM       | NET_5   | UDP echo server            |       11.73        |       10      |  1/1  |
| OK     | K64F    | ARM       | NET_6   | UDP echo client            |       12.14        |       10      |  1/1  |
| OK     | K64F    | ARM       | NET_7   | HTTP client hello world    |        23.3        |       15      |  1/1  |
| OK     | K64F    | ARM       | NET_8   | NTP client                 |       13.01        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | NET_1   | TCP client hello world     |       11.72        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | NET_13  | TCP client echo loop       |       10.41        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | NET_2   | NIST Internet Time Service |       10.24        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | NET_3   | TCP echo server            |        9.8         |       10      |  1/1  |
| OK     | LPC1768 | ARM       | NET_4   | TCP echo client            |        9.84        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | NET_5   | UDP echo server            |        9.58        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | NET_6   | UDP echo client            |        9.86        |       10      |  1/1  |
| OK     | LPC1768 | ARM       | NET_7   | HTTP client hello world    |       15.46        |       15      |  1/1  |
| OK     | LPC1768 | ARM       | NET_8   | NTP client                 |       10.13        |       10      |  1/1  |
+--------+---------+-----------+---------+----------------------------+--------------------+---------------+-------+
Result: 18 OK

Completed in 234.56 sec
```