DarkRadiant shader system

The DarkRadiant shader system module is initialised during DarkRadiant startup and parses the material files during this phase.

It consists of several vital components:

• The ShaderLibrary which holds all the named ShaderDefinitions and named Shader objects.
• The GLTextureManager, responsible for "realising" the actual Texture objects (this includes image post-processing like gamma-adjustment and resampling).