Latex in docstrings

[fzimmermann89]

We currently use a mix of latex and non-latex in docstrings for equations.

This is a balance between readability in source code,\mathbb{R} \rightarrow \mathbb{R} is quite difficult to read compared to R-> R

@koflera's argument is, that either way you would not look at equations in vscode's popup messages or in code, but that it is more important that the equations look ok in the documentation.

Maybe we should check for the equations we currently have again how they look in docu.