allow users by role/name

[mwfarb]

We currently allow users have a presence and to enter the scene (two different concepts) by simple boolean scene permissions. It would be better to show by role or by namespace who can enter, have an avatar, providing better granularity.

• This can be done post-topic-v5 refactor.

role	user entry	user avatar
none		scene.users=false
admin
staff
owner
editor
authenticated	scene.anon=false
unauthenticated	scene.anon=true	scene.users=true