[vtkusers] Addition to vtkDecimatePro; vtkTriangleFilter name

[David Doria]

Instead of throwing this warning:
DecimatePro does not accept polygons that are not triangles.

would it make sense to have DecimatePro go ahead and triangulate the
input polygons if necessary? It seems to add an extra step in code as
well as in Paraview - the user must add a TriangleFilter and then a
Decimate filter in order to accomplish a single "concept" of
decimation.

Also, does anyone else think it should be called vtkTriangulateFilter
instead of vtkTriangleFilter? In Paraview the filter has been named
Triangulate and I had to go into the Paraview xml to find that it was
actually calling vtkTriangleFilter because I couldn't find
vtkTriangulateFilter.

Thanks,

David