Configure Defra mappings for import to bouncer

This is the addition of all mappings from the story https://www.pivotaltracker.com/story/show/66335764.

In order to have DEFRA manage their mappings using the transition app, we must arrange to configure the GDS app with their existing server rules and existing mappings. This pull request handles the second of these.

Once this import has run, we can configure www.defra.gov.uk as a site in the transition app, and begin to devolve DEFRA mapping activity to their users.