refs #13523. vtkPointSet and Scale filter fix.

1) Scale filter fixed to set the representation to Surface. The change to StructuredGrid as the type for vtkasscicated with MDHistoWorkspaces seems to have broken this.

2) Scale filter fixed to work with vtkPointSets rather than vtkUnstructuredGrids. This makes the algorithm very generic, and removes the need to convert vtkPolyData sets into vtkUnstructuredGrids, as was happening previously.