Form element annotation builder: `ToMany` and `ToOne` support

Adds `*ToMany` and `*ToOne` support to the [`DoctrineORMModule\Form\Annotation\ElementAnnotationsListener`](https://github.com/doctrine/DoctrineORMModule/blob/master/src/DoctrineORMModule/Form/Annotation/ElementAnnotationsListener.php)

Cleaned up version of #191