Removed the LevelChunk class

LevelControl now treats all spatials equally, and checks each one for
removal. No objects of importance need to be grouped together, so the
LevelChunk class is scrapped. Lights belonging to a single chunk is
currently not supported. The Node containing the background acts as a
checkpoint node – its destruction due to out-of-bounds triggers the
creation of a new chunk of the level.
Removed LevelChunk class part 2

Missed including files in commit
ab45071df1323b35303d9726116f0f2b6b5c27bd