Add PRM informations on /routes

[pbougue]

For PRM information, one might want to display which stop_point is PRM-available, and some indicators on routes using that stop_point (to know if a PRM can hope to get on board line 45 toward Papeete town center at the Railway station).
One idea is to add a sub-object to routes (on 10 days, if only 1 circulation on 10 is PRM-available):

{
  "routes": {
    "vehicle_journeys_statistics": {
      "nb_vehicle_journey_day_prm": 10,
      "nb_vehicle_journey_day_not_prm": 90,
      "nb_vehicle_journey_day_total": 100
    }
  }
}

We would output the number of circulations*nb of day each one circulate in each field