Message Relay Foundation

Now that we have lots of possible devices in the game, we need a nice message relay infrastructure.
This commit introduces a first foundation for this:

- The webserver should act only as a mere message relay
	- Current problem: The webserver needs to know the identifier of remote devices, so he needs to intercept the “remoteidentifier” message - is there any way around this?
	- Native layer and remote devices cannot communicate: Native layer or remote device messages are always relayed to the weblib
	- Weblib messages have a “target” property that can be either “native” or “remote”, telling the webserver where to relay the message to. If it is remote, it needs a “targetIdentifier” property as well

- The web application can now register for “deviceConnected” and “connectionRequestFailed” events