[opm][geometry] Correct opm-grid patch

Adapt geometry() functions of opm-grid

patches/opm-grid-2017.04.patch

 diff --git a/dune/grid/cpgrid/Entity.hpp b/dune/grid/cpgrid/Entity.hpp
-index eadcb33..290fbb0 100644
+index eadcb33..0efcedd 100644
 --- a/dune/grid/cpgrid/Entity.hpp
 +++ b/dune/grid/cpgrid/Entity.hpp
+@@ -148,7 +148,7 @@ namespace Dune
+             }
+ 
+             /// Returns the geometry of the entity (does not depend on its orientation).
+-            const Geometry& geometry() const;
++            Geometry geometry() const;
+ 
+             /// We do not support refinement, so level() is always 0.
+             int level() const
 @@ -182,7 +182,7 @@ namespace Dune
              /// The count of subentities of codimension cc
              unsigned int subEntities ( const unsigned int cc ) const
@@ -11,6 +20,15 @@ index eadcb33..290fbb0 100644
                  if (cc == 0) {
                      return 1;
                  } else if (cc == 3) {
+@@ -412,7 +412,7 @@ namespace Dune {
+ namespace cpgrid {
+ 
+ template <int codim>
+-const typename Entity<codim>::Geometry& Entity<codim>::geometry() const
++typename Entity<codim>::Geometry Entity<codim>::geometry() const
+ {
+     return pgrid_->geomVector<codim>()[*this];
+ }
 diff --git a/dune/grid/cpgrid/Geometry.hpp b/dune/grid/cpgrid/Geometry.hpp
 index 86d82a5..10c7e14 100644
 --- a/dune/grid/cpgrid/Geometry.hpp
@@ -68,6 +86,19 @@ index 86d82a5..10c7e14 100644
              }
  
              /// Using the cube type for all entities now (cells and vertices),
+diff --git a/dune/grid/cpgrid/Intersection.hpp b/dune/grid/cpgrid/Intersection.hpp
+index f7152ef..cf01473 100644
+--- a/dune/grid/cpgrid/Intersection.hpp
++++ b/dune/grid/cpgrid/Intersection.hpp
+@@ -188,7 +188,7 @@ namespace Dune
+             /// @brief
+             /// @todo Doc me!
+             /// @return
+-            const Geometry& geometry() const
++            Geometry geometry() const
+             {
+                 return global_geom_;
+             }
 diff --git a/dune/grid/polyhedralgrid/geometry.hh b/dune/grid/polyhedralgrid/geometry.hh
 index 64a15fc..9c3c0b4 100644
 --- a/dune/grid/polyhedralgrid/geometry.hh