New windowing system

Large commit that totally refactor of the way we handle the bar and
panels.

Testing should focus on Panels, Bar, Keyboard Focus, IPC calls.

Changes brief:
- One NFullScreenWindow per screen which handle it's bar and dedicated
panels.
- Added shadows
- Reintroduced dimming
- New panels animations
- Proper Z ordering
- Panels on overlay laywer is not reimplemented, if we do it then the
bar will be on the Overlay too
- Panel dragging was not reimplemented, to be discussed before
reimplementing
- Still a WIP, need to work more on shadows and polishing + debugging.

Modules/Settings/Tabs/ControlCenterTab.qml

@@ -40,7 +40,7 @@ ColumnLayout {
 
   // Handler for drag start - disables panel background clicks
   function handleDragStart() {
-    var panel = PanelService.getPanel("settingsPanel")
+    var panel = PanelService.getPanel("settingsPanel", screen)
     if (panel && panel.disableBackgroundClick) {
       panel.disableBackgroundClick()
     }
@@ -48,7 +48,7 @@ ColumnLayout {
 
   // Handler for drag end - re-enables panel background clicks
   function handleDragEnd() {
-    var panel = PanelService.getPanel("settingsPanel")
+    var panel = PanelService.getPanel("settingsPanel", screen)
     if (panel && panel.enableBackgroundClick) {
       panel.enableBackgroundClick()
     }