provide an online mode

[fennibay]

For debugging and development purposes an online mode would be helpful.

Workflow:

1. Prepare a Thing Description for a certain device which is available on the network
2. Go online in editdor, which switches the view to a thing viewer mode
3. Execute the InteractionAffordances on the thing: read/write/observe properties, invoke actions, subscribe/unsubscribe to events and get notifications; and show the results
4. Also provide a log view to monitor what's happening on the wire.

Restrictions:

• Support only a few selected protocols, e.g. just http for the beginning.

This could also be a separate tool complementing editdor or a plugin to it.

[fennibay]

cc @rhofer @fexpal