Make the pop-slot indicator easier to see

For worlds that are light in coloration - e.g. a Huge Desert planet - the population "Spedometer" is essentially impossible to see past "12 o'clock" - because of the lighting effect causing there to be no contrast between the population slot-indicator (spedometer / popometer?) and the planet's surface.

It would be nice to be able to see it, so that it's much easier at a glance to see how many empty slots any given world currently has.

---

Related: mousing over a world should show, e.g., "6/9" in the Population tooltip (currently it only shows, e.g. "9" - the maximum, instead of used / maximum).

---

Related: mousing over a system icon from the main map should show the sys-pop/max-sys-pop in the tooltip.