Fixed OneToOne associations

I had an issue with OneToOne associaiton when the field name is different than the attribute name.

First class:

```php
class SpecialArticle
{
    /**
     * @ORM\Id
     * @ORM\OneToOne(targetEntity="Article", inversedBy="specialArticle", cascade={"persist", "remove"})
     * @ORM\JoinColumn(name="id", referencedColumnName="id")
     */
    private $article;
}
``̀`
Second class:
``̀`php
classArticle
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\OneToOne(targetEntity="ETS\CatalogBundle\Entity\SpecialArticle", mappedBy="article", cascade={"remove"})
     */
    private $specialArticle;
}
``̀`

Note: I'm not using entity inheritance, I'm using composition pattern instead.