Problems loading old ProtocolDatas with new develop

[pcwysoc]

Describe the bug
The new version of develop introduces issues loading ProtocolDatas and associated classes from older pyGSTi versions due to circuit.py changes. I ran into this issue with pickle originally, but I am now observing it mainly with the from_dir method. Here's a demo notebook:

CircuitLoadingBug.ipynb.zip

[coreyostrove]

Thanks for the report and the notebook, @pcwysoc. I was aware of the pickle issue, and this has been fixed on #496. I am having some trouble reproducing the issue with the protocol data objects though. Could you provide a pair of specific commits for the data object generation and read-in which reproduces the issue?

[pcwysoc]

Hi @coreyostrove, this may have been a branch specific issue. I will follow up if it appears to be a larger problem.