Bug 825698 - move youtube-specific code from chrome to gaia r=jdm a=blocking+

This is the gaia-side patch for bug 825698.  It moves almost all of the youtube-specific code from b2g/components/YoutubeProtocolHandler.js and puts it in apps/video/js/youtube.js

It also adds a spinner animation to the view video activity to cover the dead time while the app is querying youtube to find the right stream to use.