Some work on Config

I did some work on the Config Section:
 
* use a class instead of inline styles to decouple the markup from the style
* added tests for config
* save the value also if I press enter in that small area, where you edit the value of a config
* Bonus commit: fix a small typo I spotted while I was running the tests

The Behaviour-change is only the enabling of the enter-keypress for saving values.