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

@@ -383,12 +383,13 @@ class Dynesty(NestedSampler):
                         "The resume file {} is corrupted or the version of "
                         "bilby has changed between runs. This resume file will "
                         "be ignored."
-                        .format(self.resume_file))
+                        .format(self.resume_file)
+                    )
                     return False
                 version_warning = (
                     "The {code} version has changed between runs. "
                     "This may cause unpredictable behaviour and/or failure. "
-                    "Old version = {old}, new version = {new}".
+                    "Old version = {old}, new version = {new}."
 
                 )
                 for code in versions: