Fixed visualClear / added clearfix

@maethu 

Replaced
`<span class="visualClear">&nbsp;</span>`
with
`<div class="visualClear"><!-- --></div>`

Also added `clearfix` class in newsblock view:
before:
![Bildschirmfoto 2013-03-18 um 14 41 18](https://f.cloud.github.com/assets/157533/270742/5d8ba6b0-8fd3-11e2-90c7-e81f3569b723.png)

after:
![Bildschirmfoto 2013-03-18 um 14 54 59](https://f.cloud.github.com/assets/157533/270751/79be0dfa-8fd3-11e2-945e-4ce7ade29a41.png)