Stats app : Parent the ScriptNode to the application root
Stats app : Parent the ScriptNode to the application root

This is where applications are expected to store their scripts, and means the `stats` app more acurately models what happens in the `gui` and `execute` apps. This exposes an interesting performance problem with the ArnoldLight node.

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