Gwork GUI DirectX 11 Renderer

I added a DirectX 11 renderer to Gwork. Thanks to Github user Topblast for the original code. I had to make a few modifications:

• The Windows DirectX SDK no longer includes the D3DX extensions. These can be used to compile shaders and load bitmaps. Instead we use the D3D API and STB image.
• The Pixel colour sampler also seemed to not read the alpha channel so instead we use the STB image that is retained. Eventually, I'd like to move all the skin config into a single data file so things are more data driven so this is somewhat temporary.
• Fixed the Gwork Windows platform. This means things like the clipboard should work.