Blender Git Loki

Render Branch: indirect light shading / bump. The bump method settings
has been removed and replaced with a shading method setting. There are
three options:

* No Shading: no bump mapping and assuming lambert shader.
* Full Shading: execute BSDF for each ray and includes bump mapping. When
combined with irradiance cache, will generally require many more samples
for bumped surfaces and execute textures 2x.
* Shade Once: execute BSDF once using averaged ligth direction for each
RGB channel. Bump mapping is also done after irradiance caching this way.
Requires fewer samples in irradiance cache and only needs to do textures
once. This is basically the trick from "An Approximate Global Illumination
System for Computer Generated Films" used by Dreamworks.

Decided to use averaged light direction instead of spherical harmonics,
uses less memory and these can be used with BSDF's. This trick is not really
accurate but seems believable enough for e.g. Minnaert and Oren-Nayar shaders,
though for example with Toon it fails to give similar results.

This commit also fixes AO falloff strength not being taken into account.