Pickle dump entire sampler in dynesty

We've noticed some pretty horrendous issues with restarting after a checkpoint recently.

I think that this is due to not saving all of the relevant state information.

This MR ensures the whole sampler will be saved.

I also took the liberty of adding two more plots.

• One is the run plot which dynesty produces, e.g.,
• The other is a little less pretty but shows the bound idx, number of likelihood calls and sampling scale as a function of the nested sampling iteration, e.g.,

The above plot shows the issue we had, the large spike followed by a higher nc steady state is when the run was interrupted and reloaded from the resume file (note that I stopped this run before it completely converged).

This is what that plot looks like with no interruption

This is what the plot looks like with the new checkpointing

bilby/core/sampler/dynesty.py

@@ -372,7 +372,7 @@ class Dynesty(NestedSampler):
         """
         from ... import __version__ as bilby_version
         from dynesty import __version__ as dynesty_version
-        versions = dict(bilby=bilby_versions, dynesty=dynesty_version)
+        versions = dict(bilby=bilby_version, dynesty=dynesty_version)
         if os.path.isfile(self.resume_file):
             logger.info("Reading resume file {}".format(self.resume_file))
             with open(self.resume_file, 'rb') as file: