MC-100: Process and normalize attribute to ApiImport format

| Q                    | A
| -------------------- | ---
| Bug fix?             | n
| New feature?         | n
| Specs pass?*         | y
| Checkstyle issues?** | n
| PMD issues?***       | n
| Fixed tickets        | MC-100
| Doc PR               | n
Imho, it's not necessary to store it here. You can directly put in setParameter method.
Unfortunately we don't have any constant for that in Akeneo PIM.