boards/arduino-mkr-common: factorize arduino-mkr boards to common place

boards/arduino-mkr-common/Makefile

boards/arduino-mkr-common/Makefile.dep

boards/arduino-mkr-common/Makefile.features

boards/arduino-mkr-common/Makefile.include

boards/arduino-mkr-common/board.c

boards/arduino-mkr-common/include/arduino_board.h

boards/arduino-mkr-common/include/arduino_pinmap.h

boards/arduino-mkr-common/include/board_common.h

boards/arduino-mkr-common/include/gpio_params.h

boards/arduino-mkr-common/include/periph_conf_common.h