Custom sort was problematic, especially with the current performance restrictions, and not really necessary as apps can just sort on the client side. That means it is not possible to sync sort settings or custom sort orders between devices, which has been deemed acceptable.
* remove sort tables from the database
* remove `readinglistorder` MW API module
* remove `/lists/order` and `/lists/{id}/order` RESTBase endpoints
* add a `sort` query parameter (or some kind of path parameter?) to `/lists/` for sorting non-deleted lists by list name (ascending) vs. sorting by last changed date (does it need reverse sortdescending)?
* does `/lists/{id}/entries/` need sort by name? How would that work exactly? (Sort by project, then by title?* add a similar parameter to `/lists/{id}/entries/` (name/date, Orname sorts by title only?)
* add corresponding sort parameters to the `readinglists` (and maybeand `readinglistentries`) endpoint
* make sure DB schema supports performant sorting