Make Louvain Clustering Seedable

[JakeSAI]

Louvain clustering is currently non-deterministic, due to random re-ordering of the agglomeration in the underlying C++ module. Passing a random seed from the top-level function down to this module would allow for reproducible clustering outputs.

Tasks:

• [ ] Fork https://github.com/dpeerlab/PhenoGraph
• [ ] Change fork to use custom implementation of https://sites.google.com/site/findcommunities/ that takes custom seed as argument
• [ ] Pass random seed argument through from top level function
• [ ] Identify and seed any other randomization invoked by phenograph using louvain

Validation:

• [ ] Verify that multiple runs with the same random seed yield identical results
• [ ] Use random seed to fix unit test results

[wbwakeman]

Superseded by #92