Used to set the target where the node is clicked to open url. It is valid when [treeNode.url exists]
Default: undefined
As same as <a> tag's 'target' attribute. e.g. '_blank', '_self' or other window name.
if this attribute is omitted, zTree default set it to '_blank'
var nodes = [
{ "id":1, "name":"test1", "url":"http://myTest.com", "target":"_blank"},
......
]