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/postProcessing/dataConversion/foamToFieldview9/foamToFieldview9.C

@@ -227,7 +227,7 @@ int main(int argc, char *argv[])
 #   include "getFieldNames.H"
 
     bool hasLagrangian = false;
-    if ((sprayScalarNames.size() > 0) || (sprayVectorNames.size() > 0))
+    if (sprayScalarNames.size() || sprayVectorNames.size())
     {
         hasLagrangian = true;
     }