Rename some files to make naming consistent

Grid_cshift.h

@@ -0,0 +1,16 @@
+#ifndef _GRID_CSHIFT_H_
+#define _GRID_CSHIFT_H_
+#include <Grid_cshift_common.h>
+
+#ifdef GRID_COMMS_NONE
+#include <Grid_cshift_none.h>
+#endif
+
+#ifdef GRID_COMMS_FAKE
+#include <Grid_cshift_fake.h>
+#endif
+
+#ifdef GRID_COMMS_MPI
+#include <Grid_cshift_mpi.h>
+#endif 
+#endif