Refactoring

I let you dig into these commits, nothing really special, it is all more or less related to **conventions** or **missing comments** and few **things we discussed earlier**.

Still, few things bothering me about the manager :
* confusion between **Doctrine EntityManager** and ours *Managers*
* the property holding the entity manager is named `entityManager` whereas we specify it as an `ObjectManager`
    * to solve this, we could have 2 abstract managers (or interfaces), one for *object* level and another for *entity* level  

The thing is definition of the property would be more consistent, but on the other hand the confusion will be greater since we would have to name these objects something like `BaseEntityManager` and `BaseObjectManager` ...