[feature] add vtk type polygon to geometry types. Grid output works, just the

type was missing.

dune/grid/io/file/vtk/common.hh

@@ -179,11 +179,12 @@ namespace Dune
       vertex = 1,
       line = 3,
       triangle = 5,
+      polygon = 7,
       quadrilateral = 9,
       tetrahedron = 10,
       hexahedron = 12,
       prism = 13,
-      pyramid = 14
+      pyramid = 14 //, polyhedron = 42
     };
 
     //! mapping from GeometryType to VTKGeometryType
@@ -203,6 +204,12 @@ namespace Dune
       if (t.isPrism()) return prism;
       if (t.isHexahedron()) return hexahedron;
 
+      if (t.isNone() )
+      {
+        if( t.dim() == 2 ) return polygon;
+        // if( t.dim() == 3 ) return polyhedron;
+      }
+
       DUNE_THROW(IOError,"VTKWriter: unsupported GeometryType " << t);
     }