fix the __load method of the proxies

[guillaumeoriol]

At this time, the persister is passed to the proxy constructor to implement lazy loading. Instead, it should be the gateway.

It also mean the Serquant\Persistence\Zend\Db\Table#loadEntity method should be refactored to pass an entity in the arguments in case of refresh.

[guillaumeoriol]

• The Zend.php class has been moved to the Zend directory and renamed Persister.php.
• A proxyNamespace option has been added to the persister
• To avoid having to change the persister constructor in the future, a Configuration class has been written that is passed to that constructor.
• A new factory has been written to simplify instantiation of the persister
• The gateway loadEntity function no longer creates the entity instance but receives it as an argument
• It is now useless to have a test for partial objects at the beginning of custom gateway loadEntity functions. But it is now mandatory to create an entity instance or a proxy instance for associations.
• The gateway is passed to the Proxy constructor instead of the persister.
• The Proxy __load and __clone functions have been changed to use the gateway instead of the persister
• A new retrieve function has been added to the gateway to encapsulate the logic that was previously in the Persister#retrieve function.
• A new newProxyInstance function has been added to the gateway that should be used by custom loadEntity functions in case of associations.