Consolidate stop/disconnect of connections

[lfse-slafleur]

Right now WebsocketConnection removes its queue from MessageRouter and ModelConnection does not.

This looks weird as I would expect MessageRouter to manage its queues. I would expect, regardless of Connection type that the connection_has_closed function in MessageRouter to be called and that is when the queue should be removed.

A connection may be stopped when a websocket disconnects, a {device,cem} model decides this should be the case or other parts of the code. Regardless of who calls it, all clean up should happen appropiately:

• Clean up queue in MessageRouter
• Stop AsyncApplication
• Delete connection from MessageRouter
• Disconnect the 'other'/reverse connection