Ability to sort items by a "Sort IDs" CSV field

[jamesvidler]

The “Sort IDs” are meant to be used as a guide to how to sort your list. It won’t always contain all your IDs – only specific ones you’ve already sorted. When you add a new item, it doesn’t explicitly add a new “ID” into the CSV.

When you are using the “Sort IDs”, you should sort by those IDs first, and then append the “unsorted” items.

It would be great to have utility function for this so that developers don't have to implement this themselves.