Done most of the base of multiple materials

The base should work, but some adjustments might be needed.
Bugfixes, but still not working

Materials are loaded and several different materials can be set up.
However, the order of the materials is not yet taken into account,
resulting in wierd stuff.
Solved bug with faces not showing up
Now shows multiple materials!

Some issues still to be solved, but ready for merge.
Merge branch 'ShaderConvertion'