Add HLSL shaders

[SaschaWillems]

Once our framework is able to load shaders from SPIR-V well start adding HLSL versions of the GLSL shaders. I will work on porting the shaders for my samples and probably some or most of he samples based on my api sample base class.

[SaschaWillems]

Quick note that with #733 now merged I started adding HLSL shaders to the first samples.

Note to myself: We should also add HLSL support to the sample documentation, maybe a small chapter on shader languages used with links to the HLSL chapters in the guide.