Enable remote "fullscreen"

It isn't true fullscreen (the js API won't allow fullscreen without user interaction) however, it will resize the video to the full width/height of the browser. If the remote browser is in fullscreen, then this essentially works as remote controlled fullscreen. It works well if you want to control an HTPC with a mobile device, or even if you just want to remotely control your HTPC. This should also allow other clients to implement remote fullscreen (if it is possible).