Initial gSet support; more cpp nodes
fix: dirty fix for one particular strange scene
fix: resolve format list
fix: better group node support; global settings under ExporterSettings
Merge branch 'dev/vray_for_blender/vb30_group' into dev/vray_for_blender/vb30
fix: more separate files
fix: return override material if needed and no material is set
fix: check visibility of effects objects