PIM-2142 : add methods to flexible query builder interface
PIM-2142 : add filter and sorter by field in flexible query builder
PIM-2142 : update calls to flexible query builder
PIM-2142 : update the changelog
PIM-2142 : add a mongo flexible query builder
PIM-2142 : fix phpdoc
PIM-2142 : add flexible query builders (orm/mongodb)
PIM-2142 : update product repository service
PIM-2142 : fix CS
Merge pull request #801 from akeneo/PIM-2142-dummy-mongo-impl

[WIP] Add a dummy MongoDB implementation of flexible query builder