The anonymous use cases for reference previews in "full" feature mode include changes to the settings dialog. Supporting code is quite complex and should be covered by tests. Let's write basic browser tests as follows:
 `includes/DevelopmentSettings.php` should enable Reference Previews "full" mode.
 All users see the cog wheel in reference popups.
 Cog wheel leads to the modal settings dialog for anons, and the appearance preferences tab for registered users.
 Settings dialog includes the "reference previews" setting.
 Changing this setting is sticky, lasts across pageviews.
 Footer is visible whenever either page or reference previews is disabled and enablement is allowed.
 Registered users don't see the cog wheel.