title: Adding metadata to jsTree
body: <p>I just can not figure this out, or find any docs.</p>
  
  <p>I have a bare-bones JSON:</p>
  
  <p>{
    "data": "node",
    "metadata" : { "content": "hellooooo" }
  }</p>
  
  <p>This gets loaded, but I can not figure out how to write to this field, retrieve this field, and ensure that it is made when a new node is created.</p>
  
  <p>Where are the docs for metadata?</p>
  
  <p>Thanks,
  Marco.</p>