title: NSManagedObject ignores return value of automaticallyNotifiesObserversForKey: ands KVO notifications
body: <p>I noticed that changing a managed property in a subclass of <code>NSManagedObject</code> sends <code>KVO</code> notifications, even if I overwrite the <code>automaticallyNotifiesObserversForKey:</code> to return NO.</p>
  
  <pre><code>+(BOOL)automaticallyNotifiesObserversForKey:(NSString *)key{
      return NO;
  }
  </code></pre>
  
  <p>Is this the expected behaviour?</p>
  
  <p>If I change a non-managed property, everything works as expected (no notification is sent).</p>
  
  <p>What's going on and why the difference between managed and non-managed properties?</p>