GTFS: timezone deactivation

for the moment we ahve to better handle stoptime (for the moment they
are stored as uint and they might overflow when the utc offset is
applied)

so timezone are hardcoded as utc to wait for the patch
Gtfs: deactivate timezone handling

we have still some problems with the timezone handling, so we want to
deactivate it for the moment.

for dumb patch is to consider that all data are in utc so no vj split is
done and no utc offset is applied
Merge pull request #512 from antoine-de/timezone_deactivation

Timezone deactivation