Add unarchiving task

https://www.agileplannerapp.com/boards/173808/cards/8018

Provides a simple way to 'unarchive' Editions by creating a draft version and force publishing it.
See discussion here https://www.agileplannerapp.com/boards/173808/discussions/2428 for more background.
Rather than passing in an email address of a specific user, it might be better to perform this action as the anonymous "GDS Inside Government Team" user (ID 406).