PIM-3531: rename AttributeHelper to AttributeValidatorHelper
PIM-3531: check existing locale and scope in AttributeValidatorHelper
PIM-3531: rework exceptions for invalid locale or scope in updaters
PIM-3531: rework exceptions for invalid locale or scope in copiers
PIM-3531: remove useless method from setters
PIM-3531: allow copiers to be able to copy from/to different types of data
PIM-3531: fix AttributeValidatorHelper
PIM-3531: fix cs
PIM-3531: fix Behat mass edit
Merge pull request #1925 from akeneo/PIM-3535

PIM-3535: enhance updaters controls
PIM-2451 : first POC of product template storage
PIM-2451 : declare denormalizers, hot fix the product value and media
PIM-2451 : update the demo command
PIM-2451 : add a detacher to detach an object
PIM-2451 : fix the error msg
PIM-3530 : re-work the group saver to prepare the appliance of template
on products
PIM-3530 : split command
PIM-3542 : add a ProductTemplateInterface and make the relation
unidirectional
PIM-3530 : add a product template updater
PIM-2455 : POC mark values as coming from a variant group in product
form