Formatting fixes and mean density in the System Editor

[zonkmachine]

Some fixes in physical descriptions.

• Introducing a space before the unit. This was in response to the formatting of objects in the system overview but Format is called elsewhere. I have looked for possible issues in other modules but so far have found none. (Images)
• Quick fix to use m³ instead of m3.
• Add Mean Density to the System Editor. It's good to be able to quickly assess if the mass/volume ratio is within a reasonable
  range.

Before

Fixed

---

Some question marks.

• Density should probably have its own format to aid in translation. I backed out of this part for now.
• Mean density, as I first introduce it, is described in kg/m3. It looks like g/cm3 is the way to go for astronomical objects. This is how it's done now in the System editor. At least they should show the same. I'm looking into fixing this for the system overview too. This should possibly be done directly in CalcMeanDensity().

[zonkmachine]

Fixed up gravitational acceleration. I'm not quite sure what changes would be needed in Format for a more permanent solution.

[fluffyfreak]

I think these are good, I don't see any issues with the code 👍

[zonkmachine]

I think these are good, I don't see any issues with the code 👍

Right, I agree. Still, parts of this should probably be fixed in Format but I haven't wrapped my head around it yet. It's not a new issue though and can be fixed up later.

[zonkmachine]

I squashed it down to two commits.

[sturnclaw]

Tons per cubic meter is (AFAIK) directly equivalent to grams per cubic centimeter; i.e. the number is the same regardless of the suffix (cm3 -> m3 is a 10^6 increase, as is grams -> tons). While the SI unit is technically more correct to use, I have no preference either way.

[zonkmachine]

Tons per cubic meter is (AFAIK) directly equivalent to grams per cubic centimeter; i.e. the number is the same regardless of the suffix (cm3 -> m3 is a 10^6 increase, as is grams -> tons). While the SI unit is technically more correct to use, I have no preference either way.

I also have no preference. Right now it's t/m³ in the System Overview and g/cm³ in the System Editor. Maybe should settle for one of them? My guess is that t/m³ feels a bit more intuitive when you're dealing with something larger like a planet. At least it does to me.

[zonkmachine]

@sturnclaw I looked into changing the mean density to g/cm in this PR but I think this would need some work. Right now we're (I really as I'm the one responsible for the original addition) just using Format.Mass which is in tons and stick a /m³ to the end. To change this to g/cm we would need something like a new Format.Density to call. Also, instead of using Format.Mass, one could just use body.meanDensity and fix the format manually. Maybe I missed a way but I think adding a new Format.Density is the best way to do it.

[sturnclaw]

Adding Format.Density would be fine, as would changing the line to be ui.Format.Number(body.meanDensity, 3) .. lc.UNIT_DENSITY with UNIT_DENSITY being defined as the appropriate g/cm^3. Regardless of the tack taken, the unit suffix should ideally be a localized string for consistency (as unlikely as it is for SI units to be written differently in other languages...)

[zonkmachine]

OK. The SI unit for density (Wikipedia) is kg/m3 and that's what you get from calcMeanDensity. You need to divide with 1000 (like I did in the editor) so you get ui.Format.Number(body.meanDensity / 1000.0, 3)
I'll poke around some more with it.