* Add comp, tesc, and tese as GLSL file extensions
* Add GLSL compute shader sample
* Add GLSL tessellation control shader sample
* Add GLSL tessellation evaluation shader sample
* Remove .comp from GLSL extensions
We have to be sure that most of the .comp files on GitHub are indeed GLSL compute shaders.
* Remove GLSL compute shader sample
* Add ShaderLab language
* Update HLSL and ShaderLab grammars to latest version
* Add .shader extension back to GLSL language
* Add sample GLSL .shader files
Note that these are copies of existing GLSL samples, renamed to have
the .shader extension.
