Restyled queue controls, adding move-song-to-top buttons.
Hopefully fixed 1-off pixel errors with list bottom margins.
Added webkit grab/grabbing cursors for queued songs.
Don't show grab cursor on currently playing queued song.
Improved padding of currently-DJing music glyph icon.
Implemented song escalation button.
Disabled song escalate button if song is already next.

Also added 'next' state to queued song model.
Merge branch 'move-song-top' into dev, adding escalate-song button.

Restyled queue controls.
Added webkit grab/grabbing cursors for queued songs.