title: User editable large title in UINavigationBar
body: <p>I need to allow the users to edit the large title of a navigation bar after they tap it.</p>
  
  <p>The solution I have so far is to instantiate a UITextField and assign it as the titleView property of the nav bar. </p>
  
  <p>The problem with this solution is achieving it with the large title style. The titleView shows up in the center of the navigation bar instead of under the back button, where the large title is supposed to show. </p>
  
  <p>How can I place the UITextField over the position of the large title and mimic its appearance?</p>