Move settings menu into panel layer surface
This
- does away with xdg popup
- fixes settings menu keyboard navigtion
this is a prereq to
hide the top bar when settings fold out/shutdown popover (!484 (merged))
Due to not using a popup the settings menu currently does not close when clicking back into the app. We don't get enough information from the compositor atm to fix this and it will become a non issue with compositor global gestures hence we close the menu whenever touching into an empty area until that is fixed (phoc#82).
This also helps to move the new notification list (!463 (closed)) into a box separate from settings.
Closes #155 (closed)
Edited by Guido Gunther