Use new Router API in Rake task
Use new Router API in Rake task

- `register` has now changed to work
- `register_application` has been renamed to `register_backend` to match
  new router nomenclature
- Added new `register_guidance` task to manually register all existing
  DetailedGuide objects with the router.

robinwhittleton/whitehall,askl56/whitehall,alphagov/whitehall,hotvulcan/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,hotvulcan/whitehall,hotvulcan/whitehall,askl56/whitehall,alphagov/whitehall,alphagov/whitehall,hotvulcan/whitehall,robinwhittleton/whitehall,ggoral/whitehall,ggoral/whitehall