iot-lab_M3: rename to iotlab-m3

Makefile.include

boards/iotlab-m3/Makefile

boards/iotlab-m3/Makefile.dep

boards/iotlab-m3/Makefile.features

boards/iotlab-m3/Makefile.include

boards/iotlab-m3/board.c

boards/iotlab-m3/dist/openocd.cfg

boards/iotlab-m3/include/at86rf2xx_params.h

boards/iotlab-m3/include/board.h

boards/iotlab-m3/include/periph_conf.h

dist/tools/sniffer/README.md

examples/default/Makefile

pkg/openwsn/README.md

release-notes.txt

tests/driver_at86rf2xx/Makefile

tests/driver_isl29020/Makefile

tests/driver_lsm303dlhc/Makefile

tests/pkg_cmsis-dsp/Makefile