Fix handling of anticlockwise backtracking correction inside section (browse VJs and stop_times reversely)
Fix handling of anticlockwise backtracking correction inside
section (browse VJs and stop_times reversely)

* improve corner cases functionnaly
* improve code and maintenance
* improve perfs a bit

/!\ anticlockwise on journey (browse sections) is not correctly handled

Tisseo/navitia,Tisseo/navitia,Tisseo/navitia,Tisseo/navitia,Tisseo/navitia