Redirect Features for routeGuards

[stud0r]

It would be very helpful to provide a possibility to routeGuards for an error page in case a routeGuard evaluates to false.
This could e.g. be an login page or an page to show that the user has insufficient rights.

[CasperPas]

I've been thinking about this too, and planning to implement it in the next few days (if no one did it first).