Fixed File->Import node selection error.
Fixed File->Import node selection error.

Sometimes the imported script will add a plug to the ScriptNode, and since we can only select nodes we must filter these out when changing the selection.

This addresses the latter half of #1077.

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