Add device type to channel label

[cdjackson]

Currently channels are simply names based on their function and this can result in channels with the same label. For example, a wall switch may have both server and client endpoints - one for controlling an inbuilt relay, and one to control external functions.

I propose where applicable (eg dimmers and switches for starters) to prepend the endpoint device type to the channel label to make this potentially clearer and help differentiate these types. In this case, it would give one a label including "Dimmer switch" and one "Dimmable light" (based on observations of the device types used in a Leviton switch).

Ideally different categories might be used to distinguish this, but that likely requires changes to OH-Core.