Comment 420 for bug 733349

Fixed it for me with the help of http://askubuntu.com/questions/36433/can-i-use-the-unity-launcher-icon-to-minimize-applications-windows#436542
But it's hard to understand that this is not the standard behavior like on trisquel and even Windows.
Good luck hitting the minimize button with your finger on the touch screen of the 4k XPS13.