Basic for stencil shadow volumes.
Merge remote-tracking branch 'origin/master' into shadow

Conflicts:
	src/states/Playing.cpp
	src/states/Playing.h

Set up test environment, starting with shadow mapping (then stencil
shadows).
Added 2D output.
Started generating shadow map.
Now outputs shadow map.
ToDo: add shadow coords (vertices in shadow camera space).
Yeha...
Works!
Optimized rendering.
Added class for shadow mapping.
Merged light sources.
Updated docu.

Now need to switch to render buffer and put it all together.
There are still a few problems with setting up a orthogonal projection
matrix.
Removed unnecessary iostream.
Moved shadow mapping to its own class.