destineo return less alternatives fallback journeys

We only want one journey with a alternative fallback, the bss has the
priority, then the bike. We take all the non_pt solutions

Refer to: http://jira.canaltp.fr/browse/NAVITIAII-1348
destineo: don't filter in debug mode
jormungandr: refacto of helpers
Merge pull request #728 from kinnou02/destineo_less_alternative

destineo return less alternatives fallback journeys