dico stats

The goal of this Merge Request is to add the new subcommand stats to dico.

The branch dico-stats-rebased is a refactored version of the dico-stat branch in repo https://gitlab.info.uqam.ca/goulet.nicolas/dico.
Differences consist mainly in regroupment of small atomic commits into more functionally significant units, plus minimal retrofits of external modifications to allow successful execution of continuous integration pipelines.