Add logout button that stops all peerconnections, restyle settings

* Update settings menu style: add 1 logout button, display image (if available), name, connected network
* Changed logout in uProxy core to stop any peerconnections
* Change UI loggedIn logic to use a ui.onlineNetwork field.  Binding to a function (loggedIn) wasn't re-evaluating when necessary and didn't give us any information about which network we are logged into (currently only 1 supported).
* Fixed bug when sending USER_SELF message to UI (had been calling flushQueuedInstanceMessages which is no longer implemented and threw a silent error)

Tested in grunt test, with new tests for syncNetwork_ in ui