this removes the per desktop profile config and replaces it with a
per-screen one that is tied to a specific display so it is far more
logical than per desktop. this allows e to set up different scaling
per screen for apps that use elementary for example via this derived
profile.
this of course is slightly problematic for e itself since it now uses
elm - as this will cause e to go kind-of-crazy with differing profiles
as it fights with itself and elm if 2 screens have different profiles.
this requires elm to be fixed to allow custom profiles per window.
this also currently won't switch profile of a window when you
reconfigure screens.
@feature
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