[feature/downlink] Take care of duty cycles of gateway in router
[feature/downlink] Take care of duty cycles of gateway in router

mgranberry/ttn,jvanmalder/ttn,TheThingsNetwork/ttn,jvanmalder/ttn,mgranberry/ttn,LoRaWanSoFa/ttn,mgranberry/ttn,TheThingsNetwork/ttn,LoRaWanSoFa/ttn,jvanmalder/ttn,TheThingsNetwork/ttn