account permission upgrade

[Hecrer]

allow admins to control the specific permissions of their user groups through some multi select or checkbox system.

[cj123]

I see this working as follows:

features register themselves as having certain permissions, through some kind of init call maybe:

func init() {
  RegisterPermission("system_logs", "View system logs")
}

these can be used to generate the permissions page.

We then define groups with a name and a page of tickboxes for all registered permissions. Users can be added to these groups.

Finally, there'd be a

user.HasPermission("system_logs") 

call or similar

[cj123]

linking #242 as a duplicate of this so we remember to do it here