Introduce csv row validator interface
Add optional csv row validation in csv reader
Fix used validator interface
Add attribute option validator (csv row)
Configure a attribute option validator and inject it in a dedicated csv
reader service
Add validation constraints for attribute, code and is_default on a row
that describes an attribute option
Introduce abstract validator to centralize the validation and skip process
Add an attribute csv row validator
Configure the attribute validator, refactor not blank and boolean
validation
Remove useless statements
Refactor boolean and not blank validation
Add dedicated reader service for each import, remove csv validator for
now
Merge branch 'master' into csv_readers
Merge pull request #500 from akeneo/csv_readers

Dedicated csv readers services