ENH: handle manifold cells in VTK, Ensight output (#2396)

- also disables PointData if manifold cells are detected.
  This is a partial workaround for volPointInterpolation problems
  with handling manifold cells.

applications/utilities/postProcessing/dataConversion/foamToVTK/convertVolumeFields.H

@@ -86,6 +86,17 @@ Description
         {
             // Use the appropriate mesh (baseMesh or subMesh)
             vtuMeshCells.reset(meshProxy.mesh());
+
+            if (doPointValues && vtuMeshCells.manifold())
+            {
+                doPointValues = false;
+                nPointFields = 0;
+                Warning
+                    << nl
+                    << "Manifold cells detected (eg, AMI) - disabling PointData"
+                    << nl
+                    << endl;
+            }
         }
 
         internalWriter = autoPtr<vtk::internalWriter>::New