Fixed styling for jquery.colorbox.

![bildschirmfoto 2014-12-02 um 10 52 30](https://cloud.githubusercontent.com/assets/1637820/5260647/732fa96a-7a11-11e4-8d5b-69fee5fb49a3.png)

New styling for colorbox in listingblock.

Ticket: https://extranet.4teamwork.ch/support/zug/maintlog/10549