Add bounding spheres

* improve intersection test on spheres
Use cursor position instead of extra target
Fix typo
Add AI

* fix cursor (now moves with mouse)
* add drawable entity (better structure)
Use render context as a parameter
Add stacking to render context
Refactor rendering pipeline

* move render helpers
* remove old test class super ball
* remove debug code
Add write access to buffer object

* add access to buffer object in vertex array objects
* add dynamic (random) starfield
Add arcade steering for turning

* remove damping for now
* rename angular force to torque
Add explosion test

* add complete update of data in buffer object
* fix cursor width