Flips on shadow casting. Adds a  Spot light.
initial stub-in: albedo. for now, straight copy-pasta of a normal diffuse in terms of methodology. altered material entry to verify functionality.
stubs for MFT_PBSRoughnessMap and MFT_PBSMetallicMap. Does nothing but generate documentation inside the hlsls at present.
Merge pull request #2 from Azaezel/physical_shading

Physical shading