[Bug] Don't apply ambient occlusion to direct lighting

[kanerogers]

Background

As @rasmusgo mentioned in #415 , we shouldn't be applying Ambient Occlusion to direct lights. I mean, it's right there in the name ambient, but I shouldn't be expected to read words or apply their meanings correctly. So I checked the spec, and (emphasis mine)..

The occlusion texture; it indicates areas that receive less indirect lighting from ambient sources. Direct lighting is not affected

Okay then. Guess we better fix it.

TODO

• Remove ambient occlusion value from direct lighting calculations