Allow popover use target elment as popover content

Example:

```htmo
<button data-toggle="popover" data-target="#popover" data-placement="bottom">Popover</button>

<div id="popover" class="popover" style="width: 500px;height: 500px;">
    <div class="arrow"></div>
     <div class="popover-content">
         Hello World
	 <a href="" data-dismiss="popover" class="pull-right">Close</a>
     </div>
</div>
```