For Issue #1318

If the text equals btn:<Text for the Button>:http://..
a hyperlink with with class btn btn-default will be shown instead of a
simple hyperlink.

It's my first pull request, so sorry if something ist not done right.

![2014-06-20 10_49_26-kibana 3 - artikelsuche](https://cloud.githubusercontent.com/assets/1630769/3338213/de88322c-f857-11e3-888c-225a3cc0cd32.png)