Optimize packet used to unload chunks for the client

At the moment telling a client to unload a chunk involves calling the entire chunk from memory, deflating it and then sending it through the pipes even though the client ignores it and based on the bitmap simply unloads the chunk, and to add the cherry on top, this is done on the main server thread.
Alternate, sync-free-but-safe chunk reference cache
Added new configuration options to enable/disable mod world generators.

Certain mods don't give players the ability to disable their world generators which can cause frustration for players trying to generate a clean world. With this update, as the server starts, all world generator registrations will automatically be added to forge.cfg with the default setting of true. To disable a mod world generator, set the modId to false and restart the server.
Merge branch 'master' of https://github.com/MinecraftPortCentral/MCPC-Plus