Meta vj

meta vj shell around vehicle journeys

It have 2 purposes:
* to store the adapted and real time vj
* sometime we have to split a vj.

  For example we have to split a vj because of dst (day saving light see gtfs parser for that)
  the meta vj can thus make the link between the split vjs

  **NOTE**: An IMPORTANT prerequisite is that ALL theoric vj have the same local time
 (even if the UTC time is different because of DST).

 That prerequisite is very important for calendar association and departure board over period
Je crois que la convention que l'on a choisi c'est rel_metavj_vj