Add "Vo" CoR estimator

About

This MR adds "Vo" CoR estimator from algotom.

Close #522 (closed)

Prior work

Close #523 (closed)

• Make CompositeCORFinder interface (i.e .init kwargs) consistent with the other CORFinder classes
  • And fix the mixing or "cor_options" and default kwargs
• Add "verbose" options to all CORFinder - either in init or find_cor() call [possibly output figure of merit]
• Rework the dispatch to be less abstruse

To do

• Add "Vo" in pipeline.COREstimator
• Unit tests
• Plug in config file
• Integrate in pipeline
• Update changelog/documentation
• End-to-end reconstruction test