samr21: initial import of file structure
samr21: fix openocd flashing script
samr21: another flash fix and added debug target
Implemented GPIO access, interrupts not supported yet
samr21: implement LED macros
Merge branch 'samr21' of https://github.com/thomaseichinger/RIOT into samr21
samr21: add missing header for m0+ CMSIS
Merge branch 'samr21' of https://github.com/thomaseichinger/RIOT into samr21
Changed terminal interface
Partially implemented gpio interrupts, also the led on the board is active-low
Implemented handlers and callback for gpio, normal gpio tested, interrupts not tested
samr21: initial import of file structure
samr21: fix openocd flashing script
samr21: another flash fix and added debug target
samr21: implement LED macros
samr21: add missing header for m0+ CMSIS
cpu/samd21: rename to correct CPU name
intermediate commit
Merge branch 'samr21' of https://github.com/thomaseichinger/RIOT into samr21

Conflicts:
	boards/atsamr21-xpro/Makefile.include
	boards/atsamr21-xpro/board.c
	boards/atsamr21-xpro/dist/flash.sh
	boards/atsamr21-xpro/include/board.h
	boards/atsamr21-xpro/include/periph_conf.h
	boards/atsamr21-xpro/system_samr21xxxA.c
changed defines