LevelChunk does not know about the physicsSpace

LevelChunk does not need a reference to the PhysicsSpace. It knows that
it might have a physicsControl of some sort.
ChunkFactory does not know about the physicsSpace

LevelControl needs to remove the chunk from the physics space anyway,
so it gets to add it to the physics space as well. This removes the
need for ChunkFactory to keep a reference to the physicsSpace – the
content can be generated (but not activated) without any physics
knowledge).
Added LevelChunk.activate()

Since the LevelChunk knows about the lights connected to it but doesn't
have them attached to itself, it has to know about its parent node
ahead of time. Thus it can also have a method for attaching itself and
all lights in one go, just like the pre-existing remove() which did the
opposite.
Removed obsolete javadoc line