Don't append port details to avrdude for usbasp

When usbasp is used as programmer, there is no need to specify the port
to avrdude.

Fix #123
Ignore commented lines while parsing boards.txt file

Fix #124
In ISP mode, read baudrate and programmer from boards.txt

Arduino IDE also reads this from boards.txt file

Fix #125
Add `burn_bootloader` target

Code to burn fuses is moved from ispload target to this new target, so
that fuses are burned only once when needed.

Fix #85
Show correct path to `arduino.mk` file in help message

Fix #120
Change echo for printf

rationale:
http://unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo

fix #129
Add common linker script for MPIDE version 0023-*-20130817-test.
Include assembly vector table in chipKIT build.

* Added build step for assembly files in CORE
* Removed duplicate flags from AS build step
Update `HISTORY.md` about ChipKIT 2013 support
Auto detect and include libraries specified in `USER_LIB_PATH`

Fix #135
Use MAKEFILE_LIST to get the name of the make file

This way we don't assume the make file is 'Makefile' and it will
work even if it is named as 'makefile' or 'makefile-uno'

Fix #130
Adjust path to avrdude/avrdude.conf for MPIDE in Linux.
Merge pull request #137 from peplin/chipkit-avrdude-mac

Adjust path to avrdude/avrdude.conf for MPIDE in Linux.
Don't append port details to avrdude for usbtiny

Fix 138
Add option to set fuses without burning a bootloader

When using ICSP programmers e.g. usbasp, you can burn sketches directly
to the chip without having to burn a bootloader, however you do need to
set fuses e.g. if you're changing speed/BOD.

Updated help text to include "make set_fuses" and also changed
"make burn_bootloader" help text which wasn't entirely accurate.

Fix #141
Merge pull request #140 from PPvG/master

Don't append port details to avrdude for usbtiny
Update changelog about `usbtiny` fix
User-defined or calculated bootloader parent directory, allows for
relative paths as defined in boards.txt  e.g. "atmega"

Also added [USER] to ARDUINO_SKETCHBOOK detection

Fixes #126
Merge pull request #142 from sej7278/master

User-defined or calculated bootloader parent directory
Update changelog about the last pull request #142