STYLE: revert bitSet/HashSet setMany() to set() method (issue #837)

- improves backward compatibility and more naming consistency.
  Retain setMany(iter1, iter2) to avoid ambiguity with the
  PackedList::set(index, value) method.

applications/utilities/mesh/advanced/refineWallLayer/refineWallLayer.C

@@ -120,7 +120,7 @@ int main(int argc, char *argv[])
         {
             const labelList& pCells = mesh.pointCells()[meshPointi];
 
-            cutCells.insertMany(pCells);
+            cutCells.insert(pCells);
         }
     }
 
@@ -153,7 +153,7 @@ int main(int argc, char *argv[])
         const polyPatch& pp = mesh.boundaryMesh()[patchi];
         const labelList& meshPoints = pp.meshPoints();
 
-        vertOnPatch.setMany(meshPoints);
+        vertOnPatch.set(meshPoints);
     }
 
     for (const label patchi : patchSet)