title: How enable/disable orientation (rotation) until press UIBarButtonItem?
body: <p>I have an application with 3 tabs in TabBarController. On the first tab, it's possible enable rotation from portrait to landscape just when the user press a button on NavigationBar? The first time the user can not rotate, only when he presses a button.</p>
  
  <p>I'm using SDK iOS 6.</p>
  
  <p>Thanks in advance!</p>