PIM-3545 Add a behat scenario to check setting different values in mass edit
PIM-3545 Update date value setter to handle null value
PIM-3545 Update media value setter to handle null value
PIM-3545 Don't apply data changed in mass edit for validation if the form is already invalid
PIM-3545 Allow null value in metric value setter
PIM-3545 Update simple select value setter to handle null value
PIM-3545 Fix undefined index in structured attribute option normalizer
PIM-3545 Allow null value in number value setter
PIM-3545 Allow null value in price value setter
Merge pull request #1954 from akeneo/null-in-setters

PIM-3545 Allow setting values to null/empty in product value setters