Simplify checking of container (List/HashTable, strings) sizes

- can use 'XX.empty()' instead of 'XX.size() == 0', 'XX.size() < 1' or
  'XX.size() <= 0' or for simpler coding.
  It also has the same number of characters as '!XX.size()' and /might/ be
  more readable

- many size checking had 'XX.size() > 0', 'XX.size() != 0', or 'XX.size() >= 1'
  when a simple 'XX.size()' suffices

applications/utilities/surface/surfaceClean/collapseBase.C

@@ -860,7 +860,7 @@ label collapseBase(triSurface& surf, const scalar minLen)
                     splitWeights
                 );
 
-                if (splitVerts.size() > 0)
+                if (splitVerts.size())
                 {
                     // Split edge using splitVerts. All non-collapsed triangles 
                     // using edge will get split.