* Don't check specific html elements from the display code (Fixes #446)

* Renamed and reworked fbuClip to clippingDisplay
* Added tests for clippingDisplay
* Use the a noVNC_container which covers the entire page to get the full size
  (Fixes #463)
* Added maxWidth and maxHeight to the canvas which can limit the viewport size
* Only show either the canvas or the logo, hide one when the other is shown
* Always center the canvas (previously it was only centered when not clipping)
* Removed iOS specific "position-fixed" fixes and start calling setBarPosition
  on every resize
* Removed the noVNC_screen_pad