Investigate upgrading nauty

[sraaphorst]

Check to see if newer versions of nauty offer faster isomorphism checking algorithms, and if so, update the version of nauty in this project from 22, which will entail:

1. Either updating the bundled nauty source code, or, if nauty has evolved far enough, unbundling the source code completely and requiring users to install it separately. (A third choice of providing the option for either could be given in the base CMakeLists.txt as well.)

2. Updating the nibac source code to support the new version of nauty.