title: Set sourceCrossOrigin to all Pictures
body: <p>I'm using Gojs 1.5.2.
  I'm loading images on my canvas from S3. the bucket has CORS.</p>
  
  <p>When I use <code>Diagram.makeImageData()</code> I get white blanks instead of my Images.
  This is explained here - <a href="http://gojs.net/latest/api/symbols/Diagram.html#makeImageData" rel="nofollow">makeImageData</a></p>
  
  <p>The solution is to use <a href="http://gojs.net/latest/api/symbols/Picture.html#sourceCrossOrigin" rel="nofollow">sourceCrossOrigin</a> to anonymous, that seems to work.</p>
  
  <p>Is there a way to define sourceCrossOrigin for all of my Picture classes in one place instead of each one of them?</p>