Show Panel on Top of Windows

Add the (not-standard) possibility to always show the Panel, with Windows below.
The idea is to enable getting rid of wasted vertical space by having the Panel applets on top of the title bar when a window is maximized. This would need the possibility to click through the panel wherever no applet is OR even better the ability to disable panelLeft and panelCenter. Automatic changing of opacity to full when a window is maximized would be good too.

This idea would work well with flipped panel mode and window buttons on the left.
This idea gets obsolet when the new GTK header bars will be used.