[parallel] Uncomment the parallel interface member functions

Communicate seems to be required by DefaultGridView. I'm not sure why this wasn't a problem before as DefaultGridView doesn't seem to have changed.

dune/foamgrid/foamgrid.hh

@@ -534,16 +534,12 @@ class FoamGrid :
             return 0;
         }
 
-
-#if 0
         /** \brief Distributes this grid over the available nodes in a distributed machine
         *
         * \param minlevel The coarsest grid level that gets distributed
         * \param maxlevel does currently get ignored
         */
-        void loadBalance(int strategy, int minlevel, int depth, int maxlevel, int minelement){
-            DUNE_THROW(NotImplemented, "FoamGrid::loadBalance()");
-        }
+        void loadBalance(int strategy, int minlevel, int depth, int maxlevel, int minelement) {}
 
         /** \brief The communication interface
         *  @param T: array class holding data associated with the entities
@@ -557,12 +553,12 @@ class FoamGrid :
         *  the protocol. Therefore P is called the "protocol class".
         */
         template<class T, template<class> class P, int codim>
-        void communicate (T& t, InterfaceType iftype, CommunicationDirection dir, int level);
+        void communicate (T& t, InterfaceType iftype, CommunicationDirection dir, int level) const
+        {}
 
         /*! The new communication interface
-
-        communicate objects for all codims on a given level
-        */
+         *communicate objects for all codims on a given level
+         */
         template<class DataHandle>
         void communicate (DataHandle& data, InterfaceType iftype, CommunicationDirection dir, int level) const
         {}
@@ -570,7 +566,6 @@ class FoamGrid :
         template<class DataHandle>
         void communicate (DataHandle& data, InterfaceType iftype, CommunicationDirection dir) const
         {}
-#endif
 
         /** dummy collective communication */
         const typename Traits::CollectiveCommunication& comm () const