Manual cleanup

[alarshi]

While looking at the ASPECT user meeting doc, I noticed that I never fixed the \si unit instances in the manual :-(.

This PR replaces these instances with .md-compatible units. I also included the python script I used, mainly to make the review easier rather than looking at the individual file changes. There were some occurrences I fixed manually, e.g., \\si{m} or \\si{meter}, but the script caught almost all of them.

I reviewed all the individual file changes but only verified that the rendering looked correct for a subset of these changes.

• I have read the guidelines in our CONTRIBUTING.md document.

For all pull requests:

• I have followed the instructions for indenting my code.

[gassmoeller]

Thanks for the work! I dont have much time to review at the moment. @danieldouglas92 or someone else could you maybe take a look at this?

[danieldouglas92]

@alarshi This is amazing! Thanks for starting the process of fixing all of the units within the manual, I also checked a few of the changes in the built docs and they render correctly, but since this (to my knowledge) is the first PR that has tried to fix the units issue, I wonder about some things that might be worth addressing to set the best precedent for future fixes of the units.

As an example, in the Gravity model section of the manual, there are units that render like this:

whereas the units that you have added here look like this:

I prefer the way that you've added your units, I like that the units are plain text and that the exponents are negative. The only thing that I would change is adding a space between the different units. I'm sure most people would know that gravity is meters per second squared, but one might read this as milliseconds ^ -2, and this would become more of an issue for things with more complicated SI units.

Also, linking the issue (#4942) that @anne-glerum started several years ago so that we can hopefully close that soon.

[alarshi]

@danieldouglas92: Thank you for the review and including the relevant issue to this PR!

That’s a good point. I agree that we should come up with a fixed style for writing the units. Right now, we are using a mix of LaTeX math mode with and without italicization, and a mix of how we include exponents, i.e., use \frac or not.
In short, these are the rendering approaches we use for units for gravity:
$m/s^2 , \quad \frac{m}{s^2}, \quad \text{m}/\text{s}^2, \quad \frac{\text{m}}{\text{s}^2}$, and what I chose for this PR: $\text{m}\,\text{s}^{-2}$ (assuming that I have added the space already between the units—thank you for the suggestion!).

Looking at the manual, most units in the material model section follow the fourth style from the list above, so we can probably be most consistent with that. Style-wise, I also like the last style, and it is also the direct conversion of the existing siunitx command.

We can bring this up in the next user meeting to decide on the style before I make any further changes (?).