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!