Improving audio/video support.

[regebro]

..raw: HTML5 audio video tags with a source works now, but at a minimum they should be tested, which they aren't, or even better, we should have ReST statements that support audio/video.

Also a way to start the audio video from the presenter console is necessary to make this really smooth. No idea of how to best do that.

[ashishguptas]

How to improve fast video load in website