Return an empty packet when command not supported

The GDB specification states that all unsupported commands should be
responded to with an empty packet.  This patch modifies the functions
handleMsg and handleQuery to return empty packets if an unknown
or unsupported command is received.  This fixes the problem where
the "C/C++ GDB Hardware Debugging" eclipse plug-in hangs when
attempting to debug.
Add extra flash sanity checks

When flashing make sure there are no overlapping write requests.
If there is an overlapping write request log it as an error but do not
overwrite the existing data.  This patch also changes the padding
value to 0xFF and converts the flash_watermark variable
to a local variable.
Merge pull request #14 from c1728p9/master

Add support for eclipse GDB
Create 0.2 release
Correct License Specifier
add script to flash nrf51822
pyOCD/gdbserver: Fixed XPSR variable name

'IPSR' was used into the code while it was reading 'XPSR'.
pyOCD/gdbserver: Fixed index out of range in lastSignal()

It happens when the debugger had been stopped in a interrupt
handler.
Merge pull request #15 from oliviermartin/gdbserver-ipsr-fixes

Fixes for GDB Server
Merge pull request #16 from xiongyihui/master

add script to flash nrf51822
Corrected so that unsupported mbed devices will be detected, and a message printed to the log. Rather than pyOCD raising an exception and dying.
Merge pull request #17 from DonMorr/master

Fix handling of unsupported mbed devices
flash_nrf51822.py uses intelhex library instead of arm-none-eabi-objcopy to deal with hex file
Merge pull request #18 from xiongyihui/master

use intelhex library instead of arm-none-eabi-objcopy to decode hex file
Fixed the issue #19 and #20
Provide a new parameter in chooseBoard, so if there is more than one board, the function will not be blocked.
Merge pull request #22 from ECNU3D/master

Fixed the issue #19 and #20, adding a new function to chooseBoard