Next/Previous open document

[GiantEnemyCrab]

While next/previous document arrow button can go to the next/previous token of the project's file sequence, I wondered if it is a good idea to also have next/previous "open" document in both annotation and curation.

This would be useful for re-annotation tasks where some of the documents get re-opened, and instead of of searching for the whole list of files for open documents, clicking an arrow in the annotation/curation UI for "next/previous open document" would jump to the open document.