title: Can't make realm List<T> conform NSCopying
body: <p>I am trying to make List&lt; T > conform NSCopying. I can't because:</p>
  
  <ol>
  <li>@objc is not supported within extensions of generic classes.</li>
  <li>I can't inherit List as it is a final class.</li>
  <li>If I implement "public func copy(with zone: NSZone? = nil) -> Any" without marking conform NSCopying. I just get error:"...copyWithZone:]: unrecognized selector sent to instance"</li>
  </ol>
  
  <p>So although there is copy() in List&lt; T >, we can never really use it.</p>
  
  <p>Current I have to make copy outside of List&lt; T >, using iteration. I can't simply using instanceOfList.copy().</p>