* Split alias levels in mentionable and messageable levels.
* Fixed some tests.
* Set messageable level to everyone by default.
* By defaults, groups are not mentionable or messageable.
* Made staff groups messageable by the system.
My discourse instance will be making regular automated public backups
of specific categories. It's preferred to be able to directly control
the path and filename of the output, rather than letting discourse
choose for me. This was already mostly supported, a filename parameter
just needed to be passed through the cli app.