Improvements in interacting with noise modeling step

[mtlam]

Discussed at our second pint_pal refactoring meeting, we want a few improvements to the noise modeling step. The first is to allow for chain_1.txt and pars.txt files needed for noise modeling to be searched for recursively within specified directories. This need not be exhaustive but will allow a little more flexibility when specifying different noise directories in a config file. The second is more complex and involves displaying warnings for "weird" noise posteriors, which we will need to specify (e.g., bumping up against a prior range). Lastly, a bug was noted that overplotting of comparison chains stopped working.

• Recursive search for chain/parameter files
• Warnings for posteriors
• Fix comparison chain plots

[jeremy-baier]

i will plan to fix the comparison chain plots. will link the PR here when it is ready for merge

[rossjjennings]

Of these, only the third item (fixing chain comparison plots) is needed for v2.0.