Shader refactor

This is the shader refactoring project as mentioned in the forum thread: http://urho3d.prophpbb.com/topic29.html

- Shader description XML's are removed. Techniques & renderpath definitions reference shader compilation parameters directly
- GLSL shaders are combined to one file (.glsl) which contains both the vertex & pixel shaders. They are called VS() and PS() similar to HLSL shaders
- ShaderCompiler utility for D3D9 mode is removed

All techniques, shaders and renderpaths / postprocesses have been converted, but not tested extensively. If you have time, please test and report any errors to this pull request. After necessary fixes I'll then merge this quite soon.