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.

applications/test/tokenize/Test-tokenize.C

@@ -53,7 +53,7 @@ int main(int argc, char *argv[])
 
     argList args(argc, argv, false, true);
 
-    const label repeat = args.opt<label>("repeat", 1);
+    const label repeat = args.get<label>("repeat", 1);
 
     const bool optVerbose = args.found("verbose");