Use peewee to replace models

Replace namedtuples by peewee models : http://docs.peewee-orm.com/en/latest/peewee/models.html

Replace .fetch & .insert calls by models usage.

Bonus point for making it a Python extra in setup.py

mentioned in issue #49 (closed)

mentioned in merge request !73 (merged)

added 3h of time spent at 2021-03-24

mentioned in issue #50

closed