RichValues 4.2

Minor update of RichValues, that mainly allows formatting rich values and adds optional improvements of the PDFs.

List of changes

• Rich values can now be formatted inside a string. For example. if x is a rich value, one can write '{:.2f}'.format(x) or f'{x:.2f}'. In this case, the main value will be displayed. One can also write float(x) or int(x), which would return the main value converted to a float or an int, respectively.
• There are two new optional parameters that allow for an alternative PDF representation of rich values with asymmetric uncertainties, based on split normal distributions and generative extreme value (GEV) distributions. It will only work for cases with amplitudes large enough and low or medium asymmetries, as explained in the user guide, and it will increase the computation time. The corresponding default parameters are use split normal distributions to model rich values and use generative extreme value distributions to model rich values. The motivation was to avoid bimodal distributions and obtain smoother shapes than with the default asymmetric bounded normal distributions. In any case, the original default PDFs are already fulfilling our requirements with respect to the median and the 1-σ confidence interval. This new feature was based on the following work by Antonio Possolo et al. (2019): https://iopscience.iop.org/article/10.1088/1681-7575/ab2a8d/.
• Minor improvements and bug fixes.