Migration for updating become-a-driving-instructor owning app and slug

become-a-driving-instructor is currently a smart-answer. It is being replaced with a simple smart-answer. This migration changes the owning app, kind and rendering app before changing the slug.
Adding detail to make messages more meaningful
Merge pull request #245 from alphagov/change_owning_app_and_slug_become_driving_instructor

Migration for updating become-a-driving-instructor owning app and slug