Merge pull request #7401 from dailab/Firefly

boards/firefly/Makefile

boards/firefly/Makefile.dep

boards/firefly/Makefile.features

boards/firefly/Makefile.include

boards/firefly/board.c

boards/firefly/doc.txt

boards/firefly/include/adc_params.h

boards/firefly/include/board.h

boards/firefly/include/gpio_params.h

boards/firefly/include/periph_conf.h

examples/lua_REPL/Makefile

tests/unittests/Makefile