Added missing default value to GafferImage::Sampler python constructor.
Added missing default value to GafferImage::Sampler python constructor.

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