Small improvements

This MR contains a couple of small improvements.

Namely making it possible to use pico-wizard packages that does not have it's own session or user and adding the users created with this package to the plugdev group, which is needed for certain functionality in at least plasma-mobile.

This MR will also add the users to the autologin group, which seems to be needed by at least nemomobile. Was requested here.

Merging this requires us to remove sddm.service from the arm-profiles in plasma-mobile and in plasma-mobile-dev.

I've split it up in 4 commits, so it's easier to cherry pick if needed.

This would ofcourse also needed to go into the pinephonepro-post-install package.

Signed-off-by: Dan Johansen strit@manjaro.org