* Support negative numbers as command option values
* Support command line options before arguments
* POSIX-compliant handling of quotes (double and single, terminated and unterminated), whitespace, hyphens, and special characters (e.g. emojis)
CommandOptions now has an IsHidden property that, when set to true, will cause the option to be hidden from the following cases:
- Help text using `-h|--help`
- Xml representations generated with the `cli xml` command
- Diagnostics displayed with the `cli explain` command
Hidden options can still be outputted with `cli explain` using the `--hidden` option that is also used to display hidden commands.
Fixes#631