White background -> simple background

BUR #7947 has been rejected.

create implication white_background -> simple_background

The wiki page for simple_background says solid color backgrounds count as simple background. So this implication makes sense

"white_background" does not have to be a "solid color background".

About "white_background vs simple_background": topic #19259.

The bulk update request #7947 (forum #200196) has been rejected by @nonamethanks.