匿名Load Panel Content
Click the refresh button on top right of panel to load content.
示例：
代码：
<div id="p" class="easyui-panel" title="Load Panel Content" style="width:700px;height:200px;padding:10px;"
data-options="
tools:[{
iconCls:'icon-reload',
handler:function(){
$('#p').panel('refresh', 'examples/panel/_content.html');
}
}]
">
</div>