Filter for Doctrine proxies

PR for #1 

Currently outputs:

```php
    myproperty: Doctrine_Proxies\__CG__\MyClass{
        _entityPersister: Doctrine\ORM\Persisters\BasicEntityPersister { ... }
        _identifier: array(1)
        __isInitialized__: false
        id: null
        expression: null
        type: null
        rootNode: null
        _algo: null
    }
```

Need to clean anything related to proxy class in the output.