Global refactoring

Changes:
* Added Storage classes to regroup all methods to query the database.
* The `lexik_translation.storage_manager` service is replaced by `lexik_translation.translation_storage` which is an instance of the right storage class.
* Remove configuation nodes about classes, all classes are now defined as parameter in the `service.xml` file.

:goberserk: :ice_cream: :cat: :cactus: