boards/iotlab: move shared code to common/iotlab

boards/common/iotlab/Makefile

boards/common/iotlab/Makefile.dep

boards/common/iotlab/Makefile.features

boards/common/iotlab/Makefile.include

boards/common/iotlab/board_init.c

boards/common/iotlab/include/board_common.h

boards/common/iotlab/include/gpio_params.h

boards/common/iotlab/include/l3g4200d_params.h

boards/common/iotlab/include/lsm303dlhc_params.h

boards/common/iotlab/include/periph_conf_common.h

boards/iotlab-a8-m3/Makefile

boards/iotlab-a8-m3/Makefile.dep

boards/iotlab-a8-m3/Makefile.features

boards/iotlab-a8-m3/Makefile.include

boards/iotlab-m3/Makefile

boards/iotlab-m3/Makefile.dep

boards/iotlab-m3/Makefile.features

boards/iotlab-m3/Makefile.include