Record/Replay improvements

[nirizr]

The following items are nice-to-haves now that basic record/replay functionality is in.

• [ ] replay multiple files in a single test run.
• [x] support replay for python 3 although record was done with python 2.
• [ ] support external execution from python 3 although IDA instance runs with python 2.
• [ ] ~Proxy classes themselves to get class attributes~ This seems unnecessary for now.
• [ ] ~return correct class proxy for __class__ attributes.~ This seems unnecessary for now.
• [ ] ~support __subclasses__, __bases__, __mro__ and the likes.~ This seems unnecessary for now.
• [ ] Selecting the proper callback recoding (if more than one) in function callback replaying?
• [ ] Include a test identifier (such as test name or index) in "instance_desc" dictionaries.
• [ ] catch replay exceptions for missing attributes or key dict names and translate them to the correct record meaning.
• [ ] Fix remaining issues with instance matching for instances involved in callbacks.