Merge pull request #79 from emilwestergren/master

Cleaned code.
Cleaned code.
Removed unused shader and unused parameter.
Removed unused shader and parameter.
Simplified vertex shader.
Removed spaces.
Added GpuTexture class.
Added OpenGLES3Texture class which implements GpuTexture .
Moved lots of code to abstract classes to make the implementations cleaner.
Changed name of upload function.
Implemented functions for setting minification and magnification filter.
Removed unused TextureBin.
Removed special case for recycling mipmapped images.
Adapted to changes in draw-gpu module.
Added some modules to export.