Add Ego-Splitting algorithm

[ArminWiebigke]

This adds the Ego-Splitting algorithm proposed by Epasto et al. (https://doi.org/10.1145/3097983.3098054).
The implementation also includes a clean-up procedure based on the OSLOM algorithm (https://doi.org/10.1371/journal.pone.0018961)

Adds two community detection algorithms:

• LouvainMapEquation: Louvain algorithm that uses the Map Equation as a fitness function (https://doi.org/10.1140/epjst/e2010-01179-1).
• LPPotts: Label propagation algorithm using the Absolute Potts Model (https://doi.org/10.1103/physreve.81.046114)

Improvements to PLP, PLM and ParallelPartitionCoarsening.

Adds some auxiliary/helper data structures.

Collaborators: @michitux @larsgottesbueren

[avdgrinten]

Thank you for the PR. I assume that you are still debugging the CI failures? Let us know when it is ready to be reviewed.

[avdgrinten]

This PR is huge. Would it be possible to break it into smaller parts? I am also not convinced that all auxiliary data structures are needed. It makes sense to add data structures that are missing in NetworKit but we should avoid duplication of data structures.

[michitux]

@larsgottesbueren and I are currently too busy to look after this but we agree that this should be split into several PRs. I will have more time starting in May to look after this, maybe @larsgottesbueren will have time before to handle the stuff he worked on.

[angriman]

@michitux @larsgottesbueren are there any updates on this PR? Is it possible to split it into smaller contributions?