migrate enums from dune-grid to dune.grid

This patch exports all enum-types defined in dune-grid (or added by
dune-python and associated to dune-grid) to the Python namespace
dune.grid.

Due to the changes in dune.grid, the PartitionIteratorType is no longer
required and, hence, is removed. It has been superseeded by the exported
partition objects.

CMakeLists.txt

 set(HEADERS
-  common.hh
   densematrix.hh
   densevector.hh
   dimrange.hh

common.hh

-// -*- tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
-// vi: set et ts=4 sw=2 sts=2:
-
-#ifndef DUNE_PYTHON_COMMON_HH
-#define DUNE_PYTHON_COMMON_HH
-
-namespace Dune
-{
-
-  namespace Python
-  {
-
-    enum class Reader { dgf, dgfString, gmsh, structured };
-    enum class VTKDataType { CellData, PointData, CellVector, PointVector };
-    enum class Marker { Coarsen = -1, Keep = 0, Refine = 1 };
-
-  } // namespace Python
-
-} // namespace Dune
-
-#endif // ifndef DUNE_PYTHON_COMMON_HH