[PropertyGrid] Improve the property editor for Point3d

[FelixGirard]

Currently, the editor for Point3d is always in meters and doesn't account for unit preference. Also, having every coordinates in the same field is not ideal.

I would really like if we could implement something more similar to what game engines are doing (but with units somewhere):

[grigasp]

Totally agree the Point2d/Point3d editor needs an overhaul. Before we can do anything, we need to know how it's expected to work:

• should it be a single input vs multiple inputs
• where should the units go,
• other...

We expect these requirements & expectations to come from consumers who're requesting the feature.