Add column option, definition in config & adapt form

Exemple for configuration :

```
chill_custom_fields:
    customizables_entities:
        -
            class: Chill\ReportBundle\Entity\Report
            name: ReportEntity
            options:
                summary_fields: {key: abc, form_type: text, form_options: { required: false }}
```

Resources/config/doctrine/CustomFieldsGroup.orm.yml

@@ -13,6 +13,8 @@ Chill\CustomFieldsBundle\Entity\CustomFieldsGroup:
         entity:
             type: string
             length: 255
+        options:
+            type: json_array
     oneToMany:
         customFields:
             orderBy: { 'ordering': 'ASC' }