feat: use gtfs

There is now a config option allowing to choose which PT schedule one wants to use between HAFAS and GTFS. Moreover, the updates in statistical matching have been implemented, it is now much faster and the age categories are matching for almost all agents. Currently implementing the possibility to choose between STATPOP and Synpop from ARE. This works in theory, but more cleaning is required. Detailed explanations can be found in CHANGELOG_aurore.md.