Cmdkit

The v2.7.1 release includes major new features along with numerous fixes and improvements.

* Automatic rich colorization of usage text with NO_COLOR support (see [no-color.org](https://no-color.org/)).
* Automatic platform support honoring conventions for Windows and macOS.
* Extensions to the standard logging module.
* Expose major features in top-level API.
* Various fixes and improvements.

- Add functionality to `Namespace` and `Configuration`
- Fix missing or broken parts of docs

Added `whereis` to `Namespace` and `Configuration`.

- Fix update behavior for Configuration
- Update documentation
- Minor fixes to code correctness

The original implementation inherited by Namespace only coerced member
mappables to a Namespace on access (read) and would clobber any in-place
changes made to the structure. Now we coerce on set (write) and so
modification works perfectly well.