add basic theming

lets the user choose between a dark theme(default) and a light with dark action bar for the counter user interface.

this is a very stupid way to do it. 
but it works

![Screenshot_2013-02-27-23-16-45](https://f.cloud.github.com/assets/1809402/202068/1760115c-8106-11e2-89dd-abc1a3727ea0.png)

sorry for the multiple commits.  
let me know what you think, even if you don't like it.