pkg/openthread: add FTD and NCP support

Makefile.dep

pkg/openthread/Makefile

pkg/openthread/Makefile.include

pkg/openthread/contrib/netdev/openthread_netdev.c

pkg/openthread/contrib/openthread.c

pkg/openthread/contrib/platform_alarm.c

pkg/openthread/contrib/platform_functions_wrapper.c

pkg/openthread/contrib/platform_logging.c

pkg/openthread/contrib/platform_misc.c

pkg/openthread/contrib/platform_radio.c

pkg/openthread/contrib/platform_random.c

pkg/openthread/contrib/platform_settings.c

pkg/openthread/contrib/platform_uart.c

pkg/openthread/include/ot.h

pkg/openthread/include/platform_config.h