title: Position a SceneKit object in front of SCNCamera's current orientation
body: <p>I would like to create a new SceneKit node when the user taps the screen, and have it appear directly in front of the camera at a set distance. For testing, this will be a SCNText reads reads "you tapped here". It should also be at right angles to the line of sight - that is, "face on" to the camera.</p>
  
  <p>So, given the <code>self.camera.orientation</code> SCNVector4 (or similar), how can I:</p>
  
  <ol>
  <li>produce the SCNVector3 that puts the node in "front" of the camera at a given distance?</li>
  <li>produce the SCNVector4 (or SCNQuaternion) that orients the node so it is "facing" the camera?</li>
  </ol>
  
  <p>I suspect that the answer to (2) is that it's the same as the  `self.camera.orientation? But (1) has me a little lost.</p>
  
  <p>I see a number of similar questions, like <a href="https://stackoverflow.com/questions/39402064/scenekit-use-transform-or-directly-manipulate-rotation-position-properties-if-g">this one</a>, but no answers.</p>