Add tests for existing global behaviour
Import whether the path should be appended
Indicate when the path is appended in a global 301
Add methods to site for global statuses

This gives a bit of consistency with Mapping and also puts the knowledge about
the contents of this field in fewer places.
Add specs for existing validations
Extra validation on global_new_url

If the path the user requested is appended to the global_new_url, it is
probably a mistake if the global_new_url includes a querystring.
Merge pull request #272 from alphagov/add_global_redirect_appending_path

Add global redirect appending path