title: detect when user take a picture or when a new image is added to the camera roll
body: <p>In my app, I have an Image View showing the most recent image from the Camera Roll.</p>
  
  <p>I want it to always be updated so I need a way to detect when a new image was added to the Camera Roll.  </p>
  
  <p>Is there a notification when user take a picture from the camera or a screenshot?
  Or even better is there a notification that a new image added to the Camera Roll? </p>