@ahfurrow => Support Phone/Bidder ID + PIN logging in

So this adds the ability for us to look up whether a bidder exists for a telephone/bidder number and then takes you to the PIN view if so. If it can't find one you're relegated to an "ask for email" view.

once you get through to the PIN view it will also log in correctlyif you have the right creds. For the next 40 minutes you can use `1111` and `1113` to log in to my stubbing account then the auction closes.

Tests may come in a later PR, feeling pushed for time now.
I think we should either set `nav` as an explicit weak variable or just do `(self.navigationController as? FulfillmentNavigationController)?.loggedInProvider = numberProvider` to avoid capturing a reference cycle.