Add widget to choose the display order of users.

All the background code was already implemented but it wasn't surfaced on the
users page.
Add widget to show deactivated users in list.

Only available to curators/admins.
Add functionality to activate users from the web app.

A button is added to the user listing for deactivated users to be activated and
the Action menu on the user's individual page now shows the correct button to
toggle the state.