title: Select Child nodes when parent is also selected in JSTREE
body: <p>I am having difficulties by selecting child nodes when parent is also selected , also would like to open subfolders and select all childs (not sure if im making it clear) so I have know how to get all the child nodes by:
    <br/></p>
  
  <pre><code>selected_nodes = $("#demo").jstree("get_selected", null, true); 
  var tree = jQuery.jstree._reference('#demo'); 
  var children = tree._get_children(selected_nodes); 
  </code></pre>
  
  <h2>  <br/>but doest really select or open child folder and nodes</h2>