ENH: add -verbose support into argList

- similar to -dry-run handling, can be interrogated from argList,
  which makes it simpler to add into utilities.

- support multiple uses of -dry-run and -verbose to increase the
  level. For example, could have

    someApplication -verbose -verbose

 and inside of the application:

    if (args.verbose() > 2) ...

BUG: error with empty distributed roots specification (fixes #2196)

- previously used the size of distributed roots to transmit if the
  case was running in distributed mode, but this behaves rather poorly
  with bad input. Specifically, the following questionable setup:

      distributed true;
      roots ( /*none*/ );

  Now transmit the ParRunControl distributed() value instead,
  and also emit a gentle warning for the user:

      WARNING: running distributed but did not specify roots!

applications/test/argList/Test-argList.C

@@ -121,6 +121,9 @@ int main(int argc, char *argv[])
     argList::addArgument("label");
     argList::noMandatoryArgs();
 
+    argList::addDryRunOption("Just for testing");
+    argList::addVerboseOption("Increase verbosity");
+
     #include "setRootCase.H"
 
     Pout<< "command-line ("
@@ -133,6 +136,10 @@ int main(int argc, char *argv[])
         << "globalPath: " << args.globalPath() << nl
         << nl;
 
+    Pout<< "dry-run: " << args.dryRun()
+        << " verbose: " << args.verbose() << nl;
+
+
     if (args.found("relative"))
     {
         Pout<< "input path: " << args["relative"] << nl