Shmem comms [NO MPI] target added. The dwf test runs and passes.

Not really shaken out to my satisfaction though as I want more tests done, so don't declare as working.
But committing my current while I try a few experimentals.

lib/communicator/Communicator_base.h

@@ -56,6 +56,8 @@ class CartesianCommunicator {
     typedef int CommsRequest_t;
 #endif
 
+    static void Init(int *argc, char ***argv);
+
     // Constructor
     CartesianCommunicator(const std::vector<int> &pdimensions_in);