匿名Initialize Value for ComboTree
Initialize Value when ComboTree is created.
示例：
代码：
<div class="easyui-panel" style="width:100%;max-width:400px;padding:30px 60px;">
<div style="margin-bottom:20px">
<input class="easyui-combotree" style="width:100%" value="122" data-options="
url:'examples/combotree/tree_data1.json',
method:'get',
label:'Select Node:',
labelPosition:'top'
">
</div>
</div>