message: Improve doc of GetFaceRestriction in parallel
diff: @@ -264,7 +264,11 @@ public:
  including the dofs for the edges and the vertices of the face. */
  virtual void GetFaceDofs(int i, Array<int> &dofs) const;
  - /// Return an Operator that converts L-vectors to E-vectors on each face.
  + /** Return an Operator that converts L-vectors to E-vectors on each face.
  + * The parallel version is different from the serial one because of the
  + * presence of shared faces. Shared faces are treated as interior faces,
  + * the returned operator handles the communication needed to get the
  + * shared face values from other MPI ranks */
  virtual const Operator *GetFaceRestriction(ElementDofOrdering e_ordering,
  FaceType type,
  L2FaceValues mul = L2FaceValues::DoubleValued
  