Video classes

[yringler]

Video should work.
In particular, if there's no audio.
In particular: Q&A: 1573
glossary: 6289

[yringler]

Some notes how to do this:
Need an abstraction for get/set position, play pause, speed
2 implementations: one for audio, one for video
Would be used in

1. audio button bar
2. progress bar

When playing, hide everything except playback buttons

1. App bar
2. parent button and title
3. description
4. favorite / share etc button row

Video would be in main player route Row, in Expanded