flow: do not navigate if neither place nor parameter has changed

[x1B]

AngularJS happily instantiates a new FlowController when $location.hash( x ) is used.
Plus, a manual history.replaceState() with only the hash changing also triggers a route change, but for some reason apparently only if there are query parameters.

We should either not run didNavigate at all if neither place nor parameter has changed, or incorporate a fragment into the navigation events, so that there is a measurable change to the place.