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/parallelProcessing/reconstructPar/reconstructPar.C

@@ -100,7 +100,7 @@ int main(int argc, char *argv[])
         args
     );
 
-    if (!timeDirs.size())
+    if (timeDirs.empty())
     {
         FatalErrorIn(args.executable())
             << "No times selected"
@@ -319,7 +319,7 @@ int main(int argc, char *argv[])
         }
 
 
-        if (cloudObjects.size() > 0)
+        if (cloudObjects.size())
         {
             // Pass2: reconstruct the cloud
             forAllConstIter(HashTable<IOobjectList>, cloudObjects, iter)