History: Orphan preferences

            New in ((Tiki25)), it permits to clean out ((Preferences)) for previously used but later removed features in Tiki.

Why is this needed? As a policy, Tiki doesn't delete data without a site admin's consent/knowledge. So when a feature is removed, what do we do with the associated data? Database tables are renamed to make it easy for an administrator to review and delete manually (or keep/move/etc.). However, preferences (configurations) are just kept in the database. So a tool like ((Adminer)) is needed to check for data and delete it. But it's tricky to what which data is no longer used. This feature permits Tiki admin to review and delete.

__As of Tiki26, please consider this feature as beta. Only use it if you are an experienced Tiki administrator.__

There is likely some data here that is actually still used, but in a non-standard way, so it fools our script.

Access at: https://example.org/tiki-admin.php?page=orphanprefs

Initial commit:
https://gitlab.com/tikiwiki/tiki/-/merge_requests/1798