Make the actual projection explicit in the LocalProjectedFEFunction

Previously, the actual projection happened by calling the constructor
of one of the classes that implements points on a manifold.  This patch
introduces an new method projectOnto, which makes the projection more
explicit.

dune/gfe/localprojectedfefunction.hh

@@ -122,7 +122,7 @@ Dune::FieldMatrix< K, m, p > operator* ( const Dune::FieldMatrix< K, m, n > &A,
       for (size_t i=0; i<coefficients_.size(); i++)
         c.axpy(w[i][0], coefficients_[i].globalCoordinates());
 
-      return TargetSpace(c);
+      return TargetSpace::projectOnto(c);
     }
 
     template <int dim, class ctype, class LocalFiniteElement, class TargetSpace>

dune/gfe/realtuple.hh

@@ -176,6 +176,15 @@ public:
         return EmbeddedTangentVector(0);
     }
 
+    /** \brief Projection from the embedding space onto the manifold
+     *
+     * For RealTuples this is simply the identity map
+     */
+    static RealTuple<T,N> projectOnto(const CoordinateType& p)
+    {
+      return RealTuple<T,N>(p);
+    }
+
     /** \brief Derivative of the projection from the embedding space onto the manifold
      *
      * For RealTuples this is simply the identity

dune/gfe/unitvector.hh

@@ -403,6 +403,13 @@ public:
         return result;
     }
 
+    static UnitVector<T,N> projectOnto(const CoordinateType& p)
+    {
+      UnitVector<T,N> result(p);
+      result.data_ /= result.data_.two_norm();
+      return result;
+    }
+
     static DerivativeOfProjection derivativeOfProjection(const Dune::FieldVector<T,N>& p)
     {
       Dune::FieldMatrix<T,N,N> result;