Minimal admin class

The minimal admin has less fields than the general RouteAdmin to provide an simpler user interface for creating routes.
This is useful when creating and editing routes in a subform in the admin class of a content document such as Symfony\Cmf\Bundle\ContentBundle\Document\StaticContent.

I guess it's quite a common case that the editor directly creates a route with a content document. In that case he doesn't want to select where the route points to - it obviously points to the content that is being created at that moment.