Allow named units to have a LaTeX representation (WIP)

[rieder]

No description provided.

[rieder]

Meant to allow for nice LaTeX representations like R_{\odot} instead of RSun

[rieder]

@spzwart @LourensVeen I'd like your thoughts on this.
The aim is to allow us to use this in e.g. axes for plots, where using "RSun" just looks stupid and manually putting in the unit leads to potential unit errors (I just found one in the book).

[LourensVeen]

Sounds like a good idea. The one thing that comes to mind is that these symbols are probably in Unicode, and that we could do that. But I'm not sure how well Unicode works in LaTeX, although it will probably work in plotting software.

Maybe something to test, it's nicer and more modern. On the other hand, LaTeX is still very widely used in science, so if Unicode doesn't solve the problem then it'll be good to have for sure.

[rieder]

Unicode can work (☉ for \odot etc), but some older LaTeX implementations don't accept unicode. Also, unicode doesn't do sub/superscript etc.
We could easily also add a unicode representation, where we write L☉ instead of LSun for example, but I think that wouldn't be as directly beneficial (matplotlib parses LaTeX, so that immediately works).