Attempt at fixing TileEntity bug

With this commit I can activate and deactivate the Redstone Jukebox
Block without losing TileEntity Data or adding it twice Server Side.

Inspired by BuildCraft TileEngine.
SMP Support (isPlaying) + Debug

implemented 2 new packets: [IsPlayingQuestion] (SERVER -> CLIENT) and
[IsPlayingAnswer] (CLIENT -> SERVER).

This will be used to check if any player in a certain area is playing a
Streaming source.
Code cleanup