This patch replaces the youTube player with a new HTML 5 video player
that can plays content hosted elsewhere.

On the backend it changes the specification of the video elements in
the course description xml file to accept the following structure:

<video> <source src="video1.mp4" type="video/mp4"/> <source
  src="video1.webm" type="video/webm"/> <source src="video1.ogg"
  type="video/ogg"/> </video>

Multiple sources are required since support from different video
containers and video format is not standarized yet among the major web
browsers.

On the frontend it replaces the previous video module with a leaner
version, controlled by modified versions of the video control
elements. Instead of interacting with the youTube API, the new
controls work directly with the HTML5 media (video and audio) API
element specification.

The new version is compatible with the previous css stylesheets.

Known Issues:
- On fullscreen the video element is not resized
- No support for subtitles yet (in the works)
- No support for multiple speeds yet (in the works)
- No support for youTube or other external video providers yet.
- No fallback to flash based video players.

course.xml if missing

choice without text caused error

  - uses multicourse settings (default_chapter and default_section)
  - it would be nice to use course_settings instead, but that is not
    currently compatible with multicourse

Course settings is in json, not python