This now shows `blueslip.error` and other JS exceptions in development
in the alert box at the top of the page. Hopefully this will make it
a lot easier to notice newly introduced JS exceptions when working on
Zulip.
Tweaked by tabbott to handle all JS errors, not just blueslip.error.
Fixes: #6155.
This refactors and fixes unicode issues where entities don't display
properly due to being a special character that seems to be rendered
incorrectly in a non-deterministic way every time.
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.