Branch/detect failure

This detects when Javascript, WebSockets, or WebGL are not enabled in the browser and prints an error message instead of embedding the app.

@jessmartin I think this could still use some design cleanup (to remove the bottom-lumps).  I'm open to suggestions.

Note: This does not detect when the network blocks a websocket connection.  That will be done in the vwf app itself (work still to come).