WST CodeTree GED Comparison

[robobenklein]

Inspired by utk-cs/CS340-Fall-2021#177 WST should have a library / common method available for comparing graphs.

Especially noting the ability to compare CodeTrees between commits and their parents, resulting in more meaningful representations of how much got changed.

Part of this might include the common library giving an endpoint to import a CodeTree into a NetworkX graph or similar, for analysis in other python libraries. Potentially the entire WST DB could be represented via a compatible python graph API, but that's a ways out.

[robobenklein]

https://networkx.org/documentation/stable/reference/algorithms/generated/networkx.algorithms.similarity.optimize_graph_edit_distance.html