Create ParsedArguments class.

To facilitate in processing command options.
Working on support for boolean single-character options for Command.
Continue working on command options.
Improve help output.
Make "--" apply only to commands with at least one other option.
Improve output of reporting commands.

Print blank line to indicate break in activity.
Raise error if user attempts switch to already-active activity.

Also raise error if user attempts to switch to inactive if already
inactive.
Made "switch" command safer.

- "swx switch" will now only create a new activity if passed the '-c' option.
- "swx switch" will now baulk if passed '-c' when the named activity already
  exists.