The shadowBuffers now handle multiple layers
The rendering is not taking the layers into consideration yet.

modified:   src/environment/Map.java
	new magic number maxLayer
modified:   src/environment/blocks/Block.java
	private to protected
modified:   src/environment/room/Room.java
modified:   src/light/LightManager.java
modified:   src/rendering/ShadowCaster.java
	modified: computeShadows
		now takes a ShadowBuffer[] rather than a ShadowBuffer