- reduces code, simplifies creation of new, specialized polyData
writers.
- new templated vtk::GenericPatchWriter, which adds support for
writing both uindirectPrimitivePatch + indirectPrimitivePatch types.
- handle geometric fields separately from regular fields with
* vtk:GenericPatchGeoFieldsWriter
* vtk:indirectPatchGeoFieldsWriter
* vtk:uindirectPatchGeoFieldsWriter