decided it's better to render objects as either surface or volume.
This may break the volume rendering patch, but shaders with volume closures still
get tagged as having volume closures, so it should be fixable without too many
changes.
* Passes renamed to samples
* Camera lens radius renamed to aperature size/blades/rotation
* Glass and fresnel nodes input is now index of refraction
* Glossy and velvet fresnel socket removed
* Mix/add closure node renamed to mix/add shader node
* Blend weight node added for shader mixing weights
There is some version patching code for reading existing files, but it's not
perfect, so shaders may work a bit different.
* Fix missing update when editing objects with emission materials.
* Fix preview pass rendering set to 1 not showing full resolution.
* Fix CUDA runtime compiling failing due to missing cache directory.
* Use settings from first render layer for visibility and material override.
And a bunch of incomplete and still disabled code mostly related to closure
sampling.