Introduce a new class "table-sticky-headers" in the settings
and organisation settings HTML table tags and it is used
to make the table headers fix at the top. This commit also
add the background-color and hover properties to the
settings and organisation settings table to make them look
similar to the recent_topics_table.
We were still sorting them with the generic alphabetic
sort due to the markup, despite passing in a custom
sort to the `list_render` class.
The `sort_email` helper often behaves like a generic
alphabetic sort, so this fix is mostly just making the code
do what it claims to do (and it's consistent with how
we already sort active users).
The nuance with emails is whether we display real
emails or system-generated emails.
We already know which list widget a `<th>`
tag is associated with when we set up the
event handler, so it's silly to read data
from the DOM to find that widget again
when the handler runs.
This commit eliminates a whole class of possible
errors and busy work.
In the emails-hidden case, for non-admins, we should remove the email
field from "Users" list in the organization settings page.
Tweaked by tabbott to correctly handle the bots and deactivated users pages.