- Remove now-removed configuration values
- Use obvious 'unset' defaults for ``project`` and ``author``
- Prefer 'e.g.' to 'ex.'
- Allow non-list sequence types in various configuration values
- Add types and defaults to every confval directive
The "alt" attribute of an `<img>` is required to convey all information.
Make it clear which logo is shown.
Also make it possible for users to override the logo_alt with a custom value.
