Check or unCheck all nodes which have been initialized. It is valid when [setting.check.enable = true & setting.check.chkStyle = "checkbox"]
This method does not trigger 'beforeCheck' or 'onCheck' callback function.
Please use zTree object to executing the method.
checked = true means: check all nodes.
checked = false means: uncheck all nodes.
Don't affect the node which 'nochecked' attribute is true.
Don't affect the node is not loaded.
no return value
var treeObj = $.fn.zTree.getZTreeObj("tree");
treeObj.checkAllNodes(true);