Media player updates

This splits the video player out into its own DOM elements making it easier to work with the video player and no longer impact audio playback, footer notifications, etc. Along with this split the css has been reworked to set explicit width/height based on viewport size, which should hopefully remove the seek flicker issue.

Just a note: the explicit size setting on android stock browser _does_ result in the video sizing beong off, but fullscreen is fine. I imagine most mobile users want to watch fullscreen anyway, so it should not be an issue.