Archive duplicate detailed guides

A validation issue on production prevented old versions being archived
when a new version of a detailed guide was published. This data
migration finds any detailed guide documents with multiple published
editions and archives the older ones.
Allow duplicate policy team email addresses
Merge pull request #939 from alphagov/detailed-guide-publishing-cleanup

Archive incorrectly published detailed guides

https://www.pivotaltracker.com/story/show/58423248
Merge pull request #941 from alphagov/allow-duplicate-policy-team-email-addresses

https://www.pivotaltracker.com/story/show/57577546