Added bootloader and boards definition for MKRFox1200 board

boards.txt

bootloaders/mkrfox1200/samd21_sam_ba_arduino_mkrfox1200.bin

bootloaders/mkrfox1200/samd21_sam_ba_arduino_mkrfox1200.hex

bootloaders/zero/board_definitions.h

bootloaders/zero/board_definitions_arduino_mkrfox1200.h

bootloaders/zero/build_all_bootloaders.sh

variants/mkrfox1200/debug_scripts/variant.gdb

...ts/mkrfox1200/linker_scripts/gcc/flash_with_bootloader.ld

...mkrfox1200/linker_scripts/gcc/flash_without_bootloader.ld

variants/mkrfox1200/openocd_scripts/arduino_zero.cfg

variants/mkrfox1200/pins_arduino.h

variants/mkrfox1200/variant.cpp

variants/mkrfox1200/variant.h