Move frontend to policy groups
Update tests for frontend
Use policy_group over policy_advisory_groups
More switching of advisory_group -> group
Remove frontend references to policy teams

They are now all groups. Teams should go, admin to follow.
Rename advisory group -> group in admin

On the frontend just display group, but use the policy_group model.
Update translations to just have group

Removed team and used the translation for `advisory_group` for `group`
some of these will want updating but it means they will at least have
something till they are updated.
Remove Policy Teams from admin

- Remove controller and views
- Remove calls to teams from policy pages
- tidy up a few calls to team on the frontend which were missed
Update test for new css selector
Fix failing cucumber

Was a little to hasty and removed the term group
Update search index for new policy-groups

Remove the old data from the index and then add the new data. The old
urls have to be hard-coded because the rails routes for the old urls has
already been deleted.
On the front end: Policy group -> group
Use groups path in the admin
Merge pull request #1404 from alphagov/policy-groups

Merge Policy Advisory Groups and Policy Teams

https://www.pivotaltracker.com/story/show/67300906