REQ/Bug: Alt tabbing when a window is fullscreen should open windows above it.

[Quackdoc]

Currently when an app is fullscreen, alt+tab will bring a new app into focus, but it is below the fullscreen app, inputs are properly sent to the app in question.

The fullscreen app should remain "fullscreen" but apps and panels should be drawn above it. This is how plasma handles it, I'm not sure how gnome does.

Partially related to #696