Add order independent single layer transparency

* move context requesting
* change test code
* add keys for adding/removing asteroids (+/- keys for now)
* remove old code
Split GUI and world rendering

* centralize uniform location
* remove automatic repositioning
Add shadow mapping prototype

* add framebuffer
* refactor OpenGL objects representing classes
* add program override to render context
* add multi-texturing (bind is automatic)
* add sphere model
* fix table model
* add depth shader
* remove unused shaders
* fix uniform names
* fix transformation in vertex classes
* fix grid circle moving with cursor