Xfce Desktop under Cooker in a VirtualBox

@rugyada @ben79

Now that I’ve had the chance to test this for a few days (first installed a Plasma image from ABF and then installed Xfce), I am very impressed. For being installed as Cooker, it has been quite stable. I’m still amazed at the seven-minute install time for the image. Using dnf to update and only using it for web browsing and e-mail, as I want to keep the created VBoxes lean, remaining mindful that (being Cooker) something could break.