Use plone default classes for table styling.

## before
![bildschirmfoto 2013-08-26 um 08 16 40](https://f.cloud.github.com/assets/157533/1024078/4298f4ce-0e19-11e3-8097-11426d6a3c30.png)

## after
![bildschirmfoto 2013-08-26 um 08 16 52](https://f.cloud.github.com/assets/157533/1024077/429ccc70-0e19-11e3-8935-9543007ecbf4.png)