ENH: consolidate handling of mandatory/optional command arguments

- for some special cases we wish to mark command-line arguments as
  being optional, in order to do our own treatment. For example,
  when an arbitrary number of arguments should be allowed.

  Now tag this situation with argList::noMandatoryArgs().
  The argList::argsMandatory() query can then be used in any further
  logic, including the standard default argument checking.

- with the new default check, can consolidate the special-purpose

      "setRootCaseNonMandatoryArgs.H"

  into the regular

      "setRootCase.H"

- revert to a simple "setRootCase.H" and move all the listing related
  bits to a "setRootCaseLists.H" file. This leaves the information
  available for solvers, or whoever else wishes, without being
  introduced everywhere.

- add include guards and scoping to the listing files and rename to
  something less generic.

     listOptions.H -> setRootCaseListOptions.H
     listOutput.H  -> setRootCaseListOutput.H

applications/utilities/mesh/manipulation/stitchMesh/stitchMesh.C

@@ -144,7 +144,8 @@ int main(int argc, char *argv[])
         "Dictionary file with tolerances"
     );
 
-    // The arguments are non-mandatory when using dictionary mode
+    // The arguments are optional (non-mandatory) when using dictionary mode
+    argList::noMandatoryArgs();
     argList::addArgument
     (
         "master",
@@ -156,7 +157,7 @@ int main(int argc, char *argv[])
         "The slave patch name (non-dictionary mode)"
     );
 
-    #include "setRootCaseNonMandatoryArgs.H"
+    #include "setRootCase.H"
 
     // We now handle checking args and general sanity etc.
     const bool useCommandArgs = (args.size() > 1);