title: Jstree: How can i avoid to check disabled checkbox?
body: <p>I have a tree in which few of the nodes are disabled.If the parent is enabled and few of its child are in disabled state and i try to check the parent node then all the nodes are checked.I want only nodes which are enabled should be checked.</p>
  
  <pre><code>$('#Tree').jstree({
      plugins: ["themes","checkbox","json_data","ui","types","real_checkboxes"],
      "checkbox" : {
          "keep_selected_style" : false,
          "tie_selection" : false,
          "three_state" : true,
          "real_checkboxes" : true
      },
      "core":
      {
          "themes": {
              "icons": false
          },
          "data":Products
      },
      "types":{
          "types":{
              "disabled" : {
                  "check_node" : false,
                  "uncheck_node" : false,
                  "select_node": false,
                  "open_node":   false,
                  "close_node":  false,
                  "create_node": false,
                  "delete_node": false
              } ,
              "directory" : {
  
                  "check_node" : false,
                  "uncheck_node" : false
              },
              "default" : { 
                  "check_node" : function () { 
                      if(node_should_be_disabled) return false; 
                      return true; 
                  }, 
                  "uncheck_node" : function () { 
                      if(node_should_be_disabled) return false; 
                      return true; 
                  } 
              } 
          } 
      }
  });
  </code></pre>