initialize_background_from_settings unnecessarily returns a changed boolean,
and compares the values itself to obtain that information. This is unnecessary,
since EelBackground already does the same. Also, by letting eel do this comparison, we can make it smarter and reload changed background images, even
if the image uri has not changed (this is a problem at the moment with the
firefox "Set as Desktop background" feature, which always writes the same file 
"Firefox_wallpaper.png").