@bhouston @WestLangley feel free to move this to a better place.

The calculation for perspective-based size attenuation of GL points was wrong; the scale should be entirely based on distance in the z-axis relative to the camera. This change makes points fit perfectly with identical quads in the same scene (where previously the point size would nonsensically shrink towards the sides of the image). A comparison can be seen here: http://imgur.com/a/G3sJ7

remove unused code (clear coat), oren-nayar, and make envmap work in world space properly while using local space coords.

fix reflectivity (it should modulate specularColor globally), fix GGX Render Equation, clean up BRDF_GGX_Environment to have incident and reflected light, pull out SpecularLightProbe.