WIP : refactor product form (associate categories part)

Todo
- [ ] fix issue category with category removal
- [ ] refactor javascript to keep only one associate script
- [ ] refactor form type to use that field for enrich and import

Bug fix: [no]
Feature addition: [no]
Backwards compatibility break: [yes]
Unit test passes: [yes]
Behat scenarios passes: [yes]
Checkstyle issues: [no]