PIM-3530 : add notes in code and template of cases supported by the
behat scenario
PIM-3530 : fix boolean scenario
PIM-3530 : fix the product prices denormalizer for multi fields case
PIM-3530 : add metric scenario
Merge pull request #1936 from akeneo/variant_group_rework_csv_denormalizers

[WIP] PIM-3530 : variant groups, re-work csv denormalizers