ENH: support 'get()' for retrieving argList options

- previously only had 'opt<..>()' for options, but 'get<..>()'
  provides more similarity with dictionary methods.
  The 'opt<..>()' method is retained.

src/OpenFOAM/db/functionObjects/functionObjectList/functionObjectList.C

@@ -403,7 +403,7 @@ Foam::autoPtr<Foam::functionObjectList> Foam::functionObjectList::New
 
     dictionary& functionsDict = controlDict.subDict("functions");
 
-    const word regionName = args.opt<word>("region", "");
+    const word regionName = args.get<word>("region", "");
 
     bool modifiedControlDict = false;