PIM-1621 : move business code from ProductValue to AbstractProductValue
PIM-1621 : move business code from Product to AbstractProduct
PIM-1621 : move business code from Atribute to AbstractAtribute
Fix CS
PIM-1621 : remove deprecated parent call
PIM-1621 : fix use statement
PIM-1621 : fix locale use statement
PIM-1621 : add missing use statement to use Family
Merge pull request #935 from akeneo/mongo/extends_entities

[WIP] Extends entities (MongoDB support)