ENH: consolidate processorTopology handling for volume and area meshes

- relocate templating to factory method 'New'.
  Adds provisions for more general re-use.

- expose processor topology in globalMesh as topology()

- wrap proc->patch lookup as processorTopology::procPatchLookup method
  (failsafe). May consider using Map<label> for its storage in the
  future.

src/finiteArea/faMesh/faPatches/constraint/processor/processorFaPatch.C

@@ -27,6 +27,7 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "processorFaPatch.H"
+#include "processorPolyPatch.H"  // For newName()
 #include "addToRunTimeSelectionTable.H"
 #include "transformField.H"
 #include "faBoundaryMesh.H"