Merge pull request #385 from rjc123/newmappings

New archive mappings for many new agencies
Merge pull request #386 from rjc123/newmappings

Add archive mappings for defra RPA
Add stub tna site to fix Transition app import

The Transition app imports redirector's data. Adding the tna_*.yml files meant
that it expected a tna.yml file to exist. When it didn't find one, the import
failed.
Merge pull request #387 from alphagov/add_tna_site_for_transition_import

Add stub tna site to fix Transition app import
Remove double underscore for bouncer
Add mappings for GAD