This works by clearing the queue, adding all the tracks from the album
to the queue and playing the first track.
Fix bug where resize might leave a play button visible
Had to refactor the QueueView somewhat as there was a bug that only
surfaced on clearing and refilling the playlist. The bug was due to the
way NSOutlineView reuses subviews.
Add screenshot with album play button
Move queue datasource and refactor view controller
Move album datasource out of the view controller
