Directed Louvain Algorithm

[BradKML]

Please use the following template to describe your feature request.
Feel free to remove those sections that do not apply to your specific request.

Is your feature request related to a problem? Please describe.
Just discovered that directed Louvain algorithm exists, yet it is not included in CDLib.

Reference.

• https://hal.archives-ouvertes.fr/hal-01231784/document
• https://github.com/nicolasdugue/DirectedLouvain
• https://github.com/graphology/graphology-communities-louvain#references

Additional Context
Directed Modularity also exists! https://igraph.org/c/doc/igraph-Community.html#igraph_modularity

[BradKML]

Other Surveys that might outline possible directed graph community detection: https://arxiv.org/pdf/1308.0971.pdf

Spectral Algorithms for Community Detection in Directed Networks https://jmlr.org/papers/volume21/18-581/18-581.pdf
Communities in directed graphs: Finding directed community structures using triads https://hal.archives-ouvertes.fr/hal-01849601v2/document

[GiulioRossetti]

Please refactor the request in #178.