Obviate need to specify vnc_auto.html and path to websocket

[ryanlovett]

We currently use the notebook extension to visit vnc_auto.html and pass in a query string parameter to set the path to the websocket. Visiting /novnc should be sufficient to get things going.

[ryanlovett]

We no longer need to explicitly visit the html landing page via 91551a6.

The parameter could be replaced by a cookie with novnc/noVNC#1055.

[ryanlovett]

Created a different PR, novnc/noVNC#1056, which would serve the websocket at the same path as noVNC's other assets. This would obviate the need to set a query string var or cookie.

[ryanlovett]

The above PRs were declined. Resubmitted as novnc/noVNC#1058 using a different approach.