fix wrong quadrature order in Poisson problem

dune/mmdg/problems/dgproblem.hh

@@ -56,7 +56,7 @@ class DGProblem
     }
 
     //returns the recommended quadrature order to compute an integral
-    //over x * boundary(x)
+    //over x * boundary(x) and K(x) * boundary(x)
     virtual int quadratureOrderBoundary () const
     {
       return 1;

dune/mmdg/problems/poisson.hh

@@ -8,6 +8,8 @@ template<class Coordinate, class Scalar = double>
 class Poisson : public DGProblem<Coordinate, Scalar>
 {
   public:
+    static constexpr int dim = Coordinate::dimension;
+    
     //the exact solution at position pos
     //1d: f(x)     = x,
     //2d: f(x,y)   = x*y,
@@ -29,6 +31,13 @@ class Poisson : public DGProblem<Coordinate, Scalar>
     {
       return true;
     };
+
+    //returns the recommended quadrature order to compute an integral
+    //over x * boundary(x) and K(x) * boundary(x)
+    int quadratureOrderBoundary () const
+    {
+      return dim;
+    }
 };
 
 #endif