WIP Adding logic fallback for image/picture/jumbotron

[haricot]

[jrief]

I somehow don't like to use random colors as fallback. Reason is that it adds a layer of unpredictability to the outcome. If a users want randomness, he shall explicitly set it.

Could you please explain what this PR does. A few lines of text would be great.

Thanks

[haricot]

The goal is to have fallbacks with the widths and heights most resembling possible. I try to redo it differently. I delete the random color which is useless because there are random x y for logos, which makes it possible to differentiate the images, as in a carousel.

[haricot]

Accurate Fallback image: (also work when resize window)

[haricot]

Accurate Fallback picture: (also work when resize window, we do not see the logos because the image origin is big)