Register contact when associated models change.
Merge pull request #155 from alphagov/register_sub_items

Register contact on save of associated items
Remove frontend routes, views and controller.

Contact detail pages are no longer served by this application, so having them
here is confusing as they are no longer in sync with the frontend app.
Helpers for frontend paths.

Enable linking from admin page to frontend, and also from frontend index page
(which is still served by this app for now) to the detail pages.
Remove test for deleted functionality.