Refactored AbstractListFragment to make it more generic and allow it to be used by
MediaFileListFragment. This adds support for switching between a single- and multicolumn
view.
Created new abstract class AbstractCursorListFragment for list fragments using a cursoradapter.
Tweaked the Now Playing and Playlist screens to better support YouTube videos
Changed HostConnectionObserver to notify clients not only when the id of what's playing changes but also when the label changes (YouTube videos and pictures for instance don't have ids, so the remote wasn't getting notified of a change in what's playing)