Improved Dispose() behavior of some Atoms.

Components can now be forcefully Disposed. This should only be used when the grid is no longer needed. This entire behavior is pointless, because whenever the Entity is disposed GC will kill the grid as well, but it looks better this way.
Essential attribute removed.

User can now remove components as he desires, the dependencies will be rechecked each time he does.
Camera now properly deals with screen resizing.