Preferences Window Sample

I wrote a small sample app to demonstrate how the preferences window (as seen in many Mac applications) can be implemented. I hope you consider this as a useful sample and add it to your sample library.

![PreferencesSample](https://f.cloud.github.com/assets/1727790/347781/0c315168-9ef4-11e2-89c2-15dd167f39b2.png)