- Trying to get rid of the distinction between "manager" and "entity
system". They're all EntityObservers now.
- Now both 'init' and 'dispose' methods are available to all entity
observers. Also added a World instance and 'process' method for all of
them.
- Had to refactor MapperImplementor and World instances a bit to get it
to compile.
- Fixed existing docs, added docs here and there, removed unused imports
in EntityObserver.
- Made 'active' field in EntityObserver private.
- Oops, forgot to remove old 'initialize' method in EntitySystem (its
superceeded by 'init' from EntityObserver).
Merge pull request #7 from dustContributor/unifiedobservers-exp

Merging unified observers branch.