title: JsTree with dnd plugin, always copy
body: <p>I have 2 trees using jsTree and dnd plugin.<br>
  I want that each drag operation to be a copy instead of a move.<br>
  There is a "copy_modifier" which works Ok when pressing a modifier key, but I want copy to be the default behavior without the modifier.
  Any ideas?</p>
  
  <p>Thanks,<br>
  Adrian</p>