timeSelector: improved functionality

- the improved side-effect of enabling -zeroTimea alters default selection
  behaviour and -latestTime selection behaviour for utilities in which
  accidentally using the 0/ directory can cause damage (eg, reconstructPar)
- can combine -time ranges and -latestTime

applications/utilities/postProcessing/dataConversion/foamToEnsightParts/foamToEnsightParts.C

@@ -74,7 +74,9 @@ using namespace Foam;
 
 int main(int argc, char *argv[])
 {
-    // with -constant and -zeroTime
+    // enable -constant
+    // probably don't need -zeroTime though, since the fields are vetted
+    // afterwards anyhow
     timeSelector::addOptions(true, false);
     argList::noParallel();
     argList::validOptions.insert("ascii", "");