(secret test)
Update on the SMP support for Redstone Jukebox

Changed TileEntity to allow correct status checks. Code now tracks if
the jukebox is Atcive (a playlist started to play), Playing (a record is
being play right now) and Powered (has redstone power).

Correctly starts and stops playing when redstone signal changes. There
is a small delay (20 ticks) to update redstone status, but I think this
is better to avoid problems like 1-tick clocks.