Mat needs the ctype, otherwise we can't switch to something other than double

[[Imported from SVN: r1010]]

grid/common/grid.cc

@@ -154,7 +154,7 @@ namespace Dune {
   }
 
   template<int dim, int dimworld, class ct,template<int,int> class ElementImp>
-  inline Mat<dim,dim>& Element<dim,dimworld,ct,ElementImp>::Jacobian_inverse (const FieldVector<ct, dim>& local)
+  inline Mat<dim,dim,ct>& Element<dim,dimworld,ct,ElementImp>::Jacobian_inverse (const FieldVector<ct, dim>& local)
   {
     return asImp().Jacobian_inverse(local);
   }

grid/common/grid.hh

@@ -333,7 +333,7 @@ namespace Dune {
     ct integration_element (const FieldVector<ct, dim>& local);
 
     //! can only be called for dim=dimworld!
-    Mat<dim,dim>& Jacobian_inverse (const FieldVector<ct, dim>& local);
+    Mat<dim,dim,ct>& Jacobian_inverse (const FieldVector<ct, dim>& local);
 
     /*! \internal
        Checking presence and format of all interface functions. With