How to add a new baryon field

If you wish to add a new BaryonField array – for instance, to track the Oxygen fraction – you’ll need to do a few things.

1. Add it to the field_type structure
2. Define it in your problem type. Adding a new Test Problem..
3. Do something with it. Adding a new Local Operator..
4. If you need to advect a species as a color field, you will have to investigate how that works. Specifically, the means of conservation – by fraction of by density – as well as the inputs into the hydro solver.