[doc] Enhance documentation of core types and interfaces
[doc] Enhance documentation of core types and interfaces

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