PBS: Made inverse square optional.
corrects misaligned texture references
Correction in comment wording.
Merge pull request #3 from Azaezel/PBS_TextureRefferences

Pbs texture refferences
Merge branch 'physical_shading' into PBS_Stubbwork
bookkeeping:
Materialfeaturetypes.h/.cpp: adds  MFT_PBSRoughness, MFT_PBSMetallic, and MFT_PBSSpecular as features.
processedShaderMaterial.cpp: switched the valuechecks from pt1 over to flipping on the overarching features.
shadergenHLSLInit.cpp: registers just roughness for now.

new code: Ok, here's how this works:
 PBSRoughnessMapHLSL::processPix now outputs (roughly) a  pbsRoughnessValue = roughnessTexture.r;
once it gets to the point where it hits PBSRoughnessHLSL::processPix, it uses that  Var *pbsRoughnessValue = (Var*)LangElement::find( "pbsRoughnessValue" ); entry to refer to it.
if not, it turns that entry into a new uniform value, whish is what is retrieved via that mPBSRoughnessValueSC = shader->getShaderConstHandle(ShaderGenVars::pbsRoughnessValue); in processedShaderMaterial

For right now, we've just got it spitting on out either the PBSRoughnessMapHLSL::processPix results + "// Getting value from PBSRoughnessMap", or "// Getting value from pbsRoughnessValue"