Added error checking to shader functions
Added attribute data function to shader
Added vertexbuffer
Added vertexbuffer test and modified shaders
Made graphics.cpp functions actually be part of the graphics class.
Merge branch 'platfrom' into core
Added test to draw a rectangle.

- Changed shaders to be more simple.
- Fixed some bugs in VertexBuffer.
- Added drawElements to VertexBuffer for testing
- Use OpenGL 2.1 so we are ES 2.0 compatible.