Remove background color options and drawing code

[zachberry]

The newest update uses background images which negates the need to draw a background single color sprite.

Need to remove any config code and drawing code relating to that background sprite.

[mholgatem]

Either solid background color or background image can be specified, But you are right about removing extraneous code; so, now a 'background sprite' is filled with the solid color, then overlayed with background image (if present) and that 'background sprite' is used rather than screen.fill -> screen.blit(background_image).

Much faster and more efficient.