title: Does Prism provide a way to cancel navigation TO a view?
body: <p>I would like to be able to block a navigation to a certain view with a password i.e. when a user wants to navigate to that view, a dialog appears and he has to type in the password first. 
  The <code>IConfirmNavigationRequest</code> interface provides a way to confirm navigation from the view/VM but not TO the view/VM.
  Is it possible to implement this using Prism?</p>