Use a splat material for the terrain in forest pond
Rearrange some things in the shader library Lighting parameters and queries are now in their own module. The Cook- Torrance BRDF has been separated from the PBR material so it's easier to use elsewhere.
Hack to work around an issue with the flat interpolation qualifier It appears that at least on my current system (GeForce 980 Ti, driver 460.91.03) vertex attributes somehow block the flat qualifier from working on the same location. It feels like a driver bug but that remains to be confirmed.
An assortment of minor fixes Mostly formatting, with a few cleanups of unnecessary things.