ENH: allow wordHashSet filter for IOobjectList::names

- simplifies usage.
  Support syncPar check on names() to detect inconsistencies.

- simplify readFields, ReadFields and other routines by using these
  new methods.

applications/utilities/preProcessing/mapFields/MapConsistentVolFields.H

@@ -51,7 +51,7 @@ void MapConsistentVolFields
 
     IOobjectList fields = objects.lookupClass(fieldType::typeName);
 
-    forAllIter(IOobjectList, fields, fieldIter)
+    forAllConstIters(fields, fieldIter)
     {
         Info<< "    interpolating " << fieldIter()->name()
             << endl;