This adds a new config value: `chorus` that signifies an instance is
more about the Reader view than individual blogs / writers. When
enabled, user navigation will show on all pages, including About,
Reader, and Privacy (ref T680).
It also uses different collection templates that keep the instance-wide
navigation at the top of the page, instead of the author's name --
again, branded more for the collective than the individual.
Ref T681
This includes:
- A new `user_invites` config value that determines who can generate
invite links
- A new page for generating invite links, with new user navigation link
- A new /invite/ path that allows anyone to sign up via unique invite
link, even if registrations are closed
- Tracking who (of registered users) has been invited by whom
It requires an updated database with `writefreely --migrate` in order to
work.
This closes T556