transmission pass and filter glossy option.
The BSDF closure class is now more similar to the SVM closures, and includes
some flags and labels that are needed to properly categorize the BSDF's for
render passes. Phong closure is gone for the moment, needs to be adapated to
the new structure still.
* Sun, area and point lights with size now supported
* Cast shadow option to disable shadow casting for lamps
* Emission strength of materials tweaked such that setting strength to 1.0
basically makes the material "shadeless" in that the value of the color
input will be the resulting color in the image.