XML-metadata-based GLSL shader framework

Slight API changes

The API has been slightly updated in order to offer a little more flexibility.

The change concerns the handling of the ZShaderManager-Singleton: its type is now a (Boost-Shared) Pointer to the KShaderManager. This means, you must access the functions through the "->" operator and not the "." operator. Furthermore, you have to EXPLICITELY initialize the pointer. The call for doing so is as follows: "SINGLETON(ZShaderManager) = KShaderManagerPtr(new KShaderManager);".

I will write a tutorial if I find some time (well, not this year).