Display correct access options for group content

Content access options for groups using members-only policy:
 - Private
 - Members of the group

Content access options for public groups:
 - Private
 - Logged in users
 - Public
 - Members of the group

In 1.8 we removed ACCESS_FRIENDS from the list but not friend collections, which is a bit irrational. Now also friend collections get leaved out.

This doesn't fix #6142 completely, so don't close it yet.