Implement cue points

[jonty-comp]

There are the 3 buttons on the bottom right of each player that don't actually do anything. It would be nice if they could be used to create a cue point so that a track could be started part way through. Even if the cue point is only stored for as long as the track is loaded that would be fine. This would allow the user to place a cue point, listen to how it sounds and then if it is OK, get back to exactly that position again.