scenario destineo: add a custom sort
scenario destineo: add a custom next/prev link system

the function "extremes" can now be on the scenario.
All of this need a big refactoring for a better integration of scenerios
and avoid a lot of code duplication: sometime we work with protobuf
object and other time with dict
scenario destineo: add tests
sceneario destineo: better testing, we don't copy all test