implement color picking from predefined set for category badges + option to change foreground color

This is a pull request to implement this:

![Screen Shot 2013-03-14 at 14 22 05](https://f.cloud.github.com/assets/1186214/258814/947b97d8-8caa-11e2-9486-6e1561b09ad0.png)

Basically, it's just adding an option to change category badge foreground color the same way that you can change background color. Plus 16 predefined colors to select from. I felt that implementing a true-color palette was too much trouble, so I implemented just this.

Let me know, how you fell about this, of course the 16 colors are pretty much random and we can change always them. Comments and critics is welcome.