Choose least used wallpaper, if there are fewer wallpapers than screens

[InsanityCode]

GnomeWallpaper/src/update-wallpaper.sh

Lines 67 to 72 in aa818b2

	num_wallpapers=$(echo "$wallpapers" | wc -l)
	if [[ $num_wallpapers -eq 1 ]]; then
	# there aren't enough wallpapers for all the screens, use the last remaining
	# TODO: use the wallpaper currently used on the least displays
	break
	fi