G5 Occupations

An occupation represents the activity of a person, ≃ the profession.
Initial occupations are defined in a csv file in data/db/occu
Groups are used to model occupations, so occupations benefit from the direct acyclic graph (DAG) structure, meaning that an occupation may have one or several parents, and one or several children. Occupations example Like for any group, one person can be associated to one or several occupations.

As a convention, a person is never associated to an occupation and its parent. For example, if a person is associated to artist and a new association to painter is added, then the association with artist becomes useless and must be removed. This is implemented by method Person::addOccus().