Improve Email View Controller

[regnerjr]

Right now is tightly coupled to its parent in 2 ways.

1. It knows for certain that the AuthDelegate will be the UIApplicationDelegate of our app. This makes them both tightly coupled. (If we want to start using the Coordinators pattern, we would have to make a special exception for this object).
2. It knows for certain that it will be pushed onto a navigation stack, we could not present this modal in certain situations, or change anything about it. We can improve this situation by calling up to some parent object "like a delegate" when interesting things happen. This will allow the delegate to do the correct thing, depending on the situation. It also gives us more power as in the "did Create a new account" scenario we can pass back the new users account.

The details can be found in the comments added on 3fd2fc6