Is the types.create_extra_permissions function deprecated?

@gregmuellegger, @rivol - I'm not seeing djadmin2 use `types.create_extra_permissions` anywhere in the project. It's not tested. It's not sampled in the example app. It's not documented. It may be superseded, especially in the face of @gregmuellegger's work on permissions, but I'm not certain.

Let me know your thoughts. If it's not needed we'll remove it. We'll have the history, so we can possibly put it's functionality back in when the time is right.