Add users / deactivate auto-registration.

[aionescu-zz]

Please add the possibility for the Admin to simply add users, and deactivate the auto-registration of new users functionality.

[thinklog]

I think that this is in fact a much needed feature, especially the request to optionally disable the auto-registration of new users.

[mcrider]

Yup, this is the next thing I'm working on (besides any actual bugs that come up in the meantime).

[mcrider]

Fixed in mcrider/azimuth-core@d44249e