Additions for sparse chunks

Hi

I have implemented some additions for sparse chunks.

* Chunk deflation is now executed asynchronously through its own ChunkTask in LocalChunkProvider
* It's now fully configurable. I have implemented a class AdvancedConfig which is reachable through org.terasology.config.Config and is serialized to json. You can configure the default tera array classes which are used to initialize new chunks and you can turn chunk deflation and logging on and off.
* The configuration is currently on game-level so it affects already saved worlds too.
* I have added a new config menu which is reachable over the settings menu in Terasology.
* The default tera array classes for sunlight, light and liquid are now 8-bit instead of 4-bit. 8-bit arrays are much faster and if chunk deflation is activated it requires less memory than 4-bit arrays without chunk deflation.

Please be very careful when you change the default settings! You can crash the game and probably damage existing worlds!

I will add a mechanism to prevent damage soon.

Panserbjoern