journeys: add the posibility to have different fallback duration for each mode

Split the "max_duration_to_pt" for each fallback mode. We keep the
"max_duration_to_pt" in the interface for not breaking the compatibily.

The the max duration for car is now set to 30 min.

The "max_duration_to_pt" field in the protobuf is keeped for compatibily
during the migration to the next version. It will be removed in another
pull request.
Merge pull request #638 from kinnou02/multiple_max_duration_to_pt

journeys: add the posibility to have different fallback duration for each mode
Disruptions: objets serialization
nav2rt: load disruptions
Disruption: change old disruption load
Disruption: handle period for at messages
Disruption: remove messages from PtObjects

Add Impacts instead of messages.

unit tests still have to be updated
Disruption: refactor old tests
Disruption: hide impacts and delete old classes
Disruption: move at_perturbation from type to ed

It is used only in ed now (for adapted), so we moved at_perturbation to
ed
Disruption: take comment into account
Adapted: corrections after review
Disruption: move a function to utils