Condense DeviceAdded/DeviceRemoved to resending DeviceList

[qdot]

Feature Description

Instead of requiring contextual messages, have DeviceList be fired for Device Added/Removed events. RequestDeviceList would have a DeviceList return with Id > 0, Added/Removed would had Id 0 (we already have context-via-Id like this for Error messages). The client can build the logic to tell the difference between what they know about and what has changed.