Stable and efficient spritebatching

Spritebatching has been fixed and the performance has been improved. One can now render 100000 textured rectangles with 600000 vertices at 60fps if the textures aren't too detailed. The plans are to make this even more efficient, but the game engine should be good enough for a first game now.

Building with small examples

YAGE builds with a small example and a few tests of the different classes.

Stable and good code

The code is now well formatted but missing a lot of features and is definitely not production ready.