[fix/#75] Add Downlink handler to the application adapter of the handler
[fix/#75] Add Downlink handler to the application adapter of the handler

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