make metadata visible in content-like views+solution

We probably want multiple solutions in the long run.

1. color card backgrounds would work.

2. Another would be to have something in the card's title bar. (This would work nicely with the title bar based solution to make simple edit-alternative to double click.) Say, an icon-sized image (e.g. "*used in code+1+image" or "*used in code+0+image"), always visible, to the left of whatever menu items (if any) are in the right corner.

It would be controlled by a setting, +*title icons (Pointer). For example, if "foo+*self+*title icons" points to "*used in code" for a card foo then if the value of "foo+*used in code" matches _2 of foo+<anything>+image, that image would be shown in icon view.

If multiple such icons are shown, the ones from the most general settings (i.e. *all+*used in code) appear right-most. If more than one emerges from the same scope, the earlier ones in the Pointer appear right-most.