Cornerplotter has args that allow calculation of only 68, 90 and 95% credible intervals, but not 99%

[DevarshiChoudhury]

xpsi/xpsi/PostProcessing/_corner.py

Line 345 in 6aeef9a

compute_all_intervals=True,

Different args, be it for printing numbers atop a corner plot, or for printing while the plot is being generated, only calculate 68, 90 and 95%. 99% interval equivalent to 3-sigma can often be quite useful as well.

(P.S. there are also missing docstrings for some of the args in some of the methods in this class.)

[thjsal]

When fixing this, I think we could add an option that would allow to calculate any credible interval defined by the user. So you would just specify if you want 98.6%, 99.0%, or whatever interval. I think that should be doable.