ENHANCEMENT: Credentials and config can arrive on websocket

[billchurch]

In the move to break the client away from the server, we should look at making the websocket capable of taking all of the parameters to start a session.

#175 was a stab at this, but too much has changed in the project to cleanly bring that in (my bad). This is a good opportunity to frame this out for 0.5.0 #244 and bring in a defined API to support it.

@nlundquist @Mierdin for comments on this