title: Constraining allowsCameraControl SCNView property to just pinch/zoom gesture
body: <p>I have a scene where, after some event, I want the user to be able to interact with the camera but just for the <code>pinch/zoom gesture</code>. I would like to enable the <code>allowsCameraControl</code> SCNView property for this purpose. </p>
  
  <p>When you enable <code>allowsCameraControl</code> all gestures are enabled, some of which aren't very intuitive to use nor easy to control. I also need to have the swipe gesture available for something different than controlling the camera. </p>
  
  <p>Is there a way to constrain the camera control to just the <code>pinch/zoom gesture</code>? In the documentation I have found a <code>SCNCameraController</code> class, but its description is extremely sparse, and haven't figured out how to use it.</p>