Arnold Renderer : Refactor attribute handling.
Arnold Renderer : Refactor attribute handling.

This just moves code around, so that the logic for attribute handling is centralised in the ArnoldAttributes class, rather than dispersed throughout the file.

hradec/gaffer,boberfly/gaffer,ivanimanishi/gaffer,GafferHQ/gaffer,chippey/gaffer,lucienfostier/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,boberfly/gaffer,hradec/gaffer,hradec/gaffer,johnhaddon/gaffer,hradec/gaffer,appleseedhq/gaffer,johnhaddon/gaffer,chippey/gaffer,hradec/gaffer,andrewkaufman/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,ivanimanishi/gaffer,andrewkaufman/gaffer,lucienfostier/gaffer,ImageEngine/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,chippey/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,chippey/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,ivanimanishi/gaffer,boberfly/gaffer,boberfly/gaffer