Changed main font to "Ubuntu"

![auswahl_043](https://f.cloud.github.com/assets/141300/821618/208c43a8-efde-11e2-9494-81ff273e8ef8.png)
![auswahl_044](https://f.cloud.github.com/assets/141300/821619/20e1fb9a-efde-11e2-9a39-38e1bd1f803b.png)