Feature/mixins

Oke, this rename annotation is made to fix problems with methods that have the same name in the API and in Forge.

You can find an example in the SpongeWorld class.

Other things that are added:
- SpongeBlock (Maded so i could test this).
- completed getWorlds() in SpongeGame (I want to remove this if needed).

Suggestion are welcome :). 
Like idk if a overwrite annotation is needed. It could be in shadow to.