Tyr: add management of scenario in tyr
jormungandr: deletion of the cheap journey computation
Jormungandr: loading of the scenario from the database

The sql query is done the first time we need the scenario, so at the
first request on a instance.
It seem that we cannot do the query during the initialization of flask
since flask-sqlalchemy need the context
Merge pull request #624 from kinnou02/config_scenario_tyr2

Config scenario tyr2