Purge pickles from report generation #655
Description
The (vast) majority of datastructures in PyGSTi have nice JSON serialization capabilities. Despite this, there are places where we save pickles to disk, as documented in #446.
We have some non-QPL Sandians suffering from pickling troubles in Report.write_notebook. I'll take care of fixing that and all other instances of pickling in report generation. I'll make the changes backward compatible so we can get them in 0.9.14.2, rather than waiting to 0.9.15.