Compare PROTEUS (grid) output to population data

[nichollsh]

This paper[1] has a really interesting comparison between a simple evolutionary model and observed exoplanet densities. They match their model input (water mass fraction) to observed density, to constrain the water mass fraction on a given planet.

We could do something similar with PROTEUS, or at least make it simple to compare model outputs to the observed population. A simple plot of planet mass/radius/density on top of the population scatter would be an interesting start. Connected to #204, #162.

The PlanetS database can be accessed here [2], and downloaded in the VOTable (XML) format here[3].

[1] https://arxiv.org/abs/2409.17394
[2] https://dace.unige.ch/exoplanets/
[3] https://dace.unige.ch/downloads/exoplanets/PLANETS.vot

[nichollsh]

Added an OSF component for storing these data (https://osf.io/fzwr4/), converted to reasonable file format and added metadata.

[nichollsh]

Requires #213 to be solved first.