Integration tests for router registraion
Add RouteableArtefact model supporting new router.

Will be used to register artefacts with the router.
Add in observer to update router after Artefact save.
Fix tests to stub out router_api where necessary
Fix cucumber to stub out router_api where necessary
Rename method and add comment for clarity
Merge pull request #93 from alphagov/router_registration

Add back router registration for new router.