Implement FlowSOM type of clustering

[mbuttner]

A popular clustering algorithm for flow cytometry data is FlowSOM. Pytometry currently only provides the scanpy clustering algorithms louvain and leiden clustering. A flowSOM type of clustering would enhance the tool.

[burtonrj]

Pinning this here for reference: https://github.com/burtonrj/CytoCluster/blob/main/cytocluster/methods/flowsom.py

Will make a PR once implemented.

[burtonrj]

As part of this work I'll also be implementing consensus clustering, as it is required for FlowSOM - for reference: https://link.springer.com/content/pdf/10.1023/A:1023949509487.pdf