Jormungandr: improvement of the pagination for journeys

The prev link search journeys who arrive before the earliest arrival.
The next link search journeys who depart after the latest departure.
SQL: fix target_metadata call
Jormungandr: allow odt
Kraken: small lint
Kraken: allow_odt only on departures and destinations
SQL: Include schema so it's detected by alembic
Merge pull request #778 from l-vincent-l/handle_metadata

SQL: fix target_metadata call
Jormungandr routing is now modular:
All route files are organised into modules in a "modules" directory.
Modules could be blueprint if need specific templates and static directories.

There is a example in modules which is desactivated by default.

Now the root index is generated dynamicaly instead of hard coded.

Test are updated accordingly
Enabled modules are now configurable in settings.py. Revert formating on instance.py. Module status and description are now in module constructor
Minor fixes. Added log
Merge pull request #779 from l-vincent-l/optimization_jp_virtual

Optimization jp virtual
Merge pull request #777 from kinnou02/better_journeys_pagination

Jormungandr: improvement of the pagination for journeys
Sql: fix leak on first alembic call
Merge pull request #780 from antoine-de/fix_alembic_leak

Sql: fix leak on first alembic call
Kraken: fix goejson of ODT section
Merge pull request #783 from l-vincent-l/NAVITIAII-1356

Kraken: fix goejson of ODT section
jormungandr: remove journey who are a lot longer that the asap journey

With the default values we remove all journeys with a duration greater
than 4 times the duration of the asap_journey + 15 minutes
Merge pull request #725 from Tisseo/dev

Routing modularization proposal
Merge pull request #784 from kinnou02/too_long_tc

jormungandr: remove journey who are a lot longer that the asap journey
vptranslator: rewrite