PIM-1370 : Add constraint on unique value for date, datetime, integer and decimal
PIM-1370 : Add some UT on unique value constraint
PIM-1370 : Clean code for unique value guesser
PIM-1370 : Change message for unique value validation
PIM-1370 : Update UT
Merge branch 'master' into PIM-1370
Merge pull request #376 from akeneo/PIM-1370

PIM-1370 : The property unique must work for date and number attributes