This better sets expectatations for the fact that in Zulip, the
Organization settings UI is available read-only to non-administrator
users.
Tweaked by tabbott to update some additional references.
For our user administration, we now primarily work with user ids
that get put into data-user-id attributes. We still put emails in the
tags to make our Casper tests easy to maintain.
This requires a minor change to the back end to pass down user ids
for the /users endpoint (in get_members_backend).
For some reason, this section of tests basically totally breaks
whatever test runs after it. To minimize the impact of that problem,
we move it to a separate file.
