Jukebox shuffling

[RaasAhsan]

Currently the jukebox plugin fetches a random from the database to play and enters it in the queue. Although a random song should have a uniform distribution, a lot of songs repeat within a couple of songs, and many songs never even get selected. We should implement a shuffle feature that is guaranteed to play every song exactly once in its queue.

Questions that need to be answered:

1. If a new song gets added, how will it be incorporated into the active shuffle, if it exists?