STYLE: use 'is_sorted()' instead of 'sorted()' for readers, Pair, ...

- avoids naming ambiguity between querying sorted state vs returning a
  sorted list (for example)

ENH: add 'good()' method to a few more classes

applications/utilities/surface/surfaceClean/collapseEdge.C

@@ -68,7 +68,7 @@ static triSurface pack
         f[1] = pointMap[f[1]];
         f[2] = pointMap[f[2]];
 
-        if (f.valid())
+        if (f.good())
         {
             newTriangles[nNewTris++] = f;
         }

applications/utilities/surface/surfaceSubset/surfaceSubset.C

@@ -117,7 +117,7 @@ int main(int argc, char *argv[])
         zoneBb.min() = markedZone[0];
         zoneBb.max() = markedZone[1];
 
-        if (!zoneBb.valid())
+        if (!zoneBb.good())
         {
             WarningInFunction
                 << "Defined zone is invalid: " << zoneBb << nl;
@@ -191,7 +191,7 @@ int main(int argc, char *argv[])
     // Faces with centre inside "zone"
     //
 
-    if (zoneBb.valid())
+    if (zoneBb.good())
     {
         Info<< "Using zone " << zoneBb << endl;