add some extra rcparams

[OriolAbril]

Description

Adds two new rcParams, data.log_likelihood and stats.ic_compare_method. Also fixes a couple of
mishaps in index_origin usage.

Checklist

• Does the PR follow official
  PR format?
• Is the code style correct (follows pylint and black guidelines)?
• Is the new feature listed in the New features
  section of the changelog?

[ahartikainen]

Logic is now wrong.

I have a model with a variable log_lik and also the correct log likelihood as log_lik2.

from_xyz(log_likelihood="log_lik2") --> log_lik goes to log_likelihood.

[OriolAbril]

True, it only has to be triggered if log_likelihood is exactly true, not if it evaluates to true, I always mess this up

[ahartikainen]

I wonder if there was something in the main that could fix that weird error.

[ahartikainen]

Yeah, when there is true (?) and no log_lik, it will of course fail, so we need to put it back to None.

[OriolAbril]

I was thinking that it may be easier to set self.log_likelihood = None and then start evaluating conditions on rcparams and log_likelihood argument to see if it needs to be updated and how. At least I don't see the current logic very clear which ends up in messing up. I'll give it a go later this evening

[OriolAbril]

nevermind, it's basically the same, it would be something like:

self.log_likelihood = None
log_likelihood = rcParams if ...  # instead of doing that on self.log_likelihood
# [...]
# keep the same conditions but using log_likelihood instead of self.log_likelihood
# skip the if isinstance(..., bool)

which is not any improvement. Let's merge like this