title: Google Cardboard SDK not containing GvrViewerMain
body: <p>Just downloaded the latest Google Cardboard SDK for Unity from here:
  <a href="https://developers.google.com/vr/unity/download" rel="nofollow noreferrer">https://developers.google.com/vr/unity/download</a></p>
  
  <p>All the tutorials I have seen (including Google's own) talk about dragging the GvrViewerMain prefab into the Hierachy.  However, I have searched all the google VR assets included in the download and GvrViewerMain is not present.  Anyone know where I can download this from or which Prefab to use instead?</p>