WIP: Add functionality for writers to translate editions

This is pretty much the simplest thing we could do to satisfy the new scenario
we've added to the editing-draft-international-priorities.feature. I'm sure
we've broken some things here but I wanted to share the branch with
@floehopper.

There's plenty more to do and I'm going to capture that in the task list of
the associated story - https://www.pivotaltracker.com/story/show/43569731