[WIP] MC-116: Add processor and normalizers for families and attribute groups

| Q                    | A
| -------------------- | ---
| Bug fix?             | n
| New feature?         | y
| Specs pass?*         | y
| Checkstyle issues?** | n
| PMD issues?***       | n
| Fixed tickets        | MC-116 / MC-83
| Doc PR               | n

WIP waiting MC-114 merge but can be commented
@willy-ahva Test it please... https://github.com/akeneo/pim-community-dev/blob/master/src/Pim/Bundle/CatalogBundle/Entity/AttributeGroup.php#L352-L357