wishlist: allow manual carousel bucket titles to be reordered

[Andrea Neiman]

This is splitting off from bug 1866406.

The fix in comment #3 of that bug enforces manual carousel order based on the order titles are added to a bucket. Copying from that comment, "For Manual carousels (as of now, without the ability to adjust the Position of items) it is the order they are added to the backing bucket. Thus emptying and refilling the bucket allows reordering."

The additional wishlist component is to add the ability for a user to intentionally order / reorder bucket titles for a manual carousel so that they can display in the specified order, rather than rely on the date added to the bucket.

[Andrea Neiman (aneiman)]

Also see related bug 1911938

[Elizabeth Thomsen (et-8)]

Just confirming that we'd still really like this enhancement! Think of the creative things we could do with this, like adding a carousel of books about the history of America (or anywhere or anything) presented in chronological order!