Support for custom find by methods

Hi,
I prepared PR, which adds a support for custom's methods from custom's class. Everything should work as well as before plus now in annotation, you can specify: 1) which entity you want and 2) class with a method which you want to use to return this entity. If it finds just one item, it returns entity, otherwise it returns array.

Sample:
```php
/**
 * 
 * @hydratatorEntity \App\Entity\Article
 * @hydratorDao \App\Dao\Articles
 * @hydratorMethod findBySlug
 */
public function actionEdit($article = null)
{
	dump($article); // entity object OR array of entity objects
}
```

If you are sure that the item will be just one, you can use type hint as before OR if it returns array, you can use array type hint.

It is without tests. If you like it, i will try to write tests.
It looks like you need filter method and you try to put that into method annotation. In such case, it would be better to move such method into model services. It would be easily extensible in the future and less magic. Also you'll probably need some other custom methods, or add order, limit, offset etc.

This extension should only hydrate (as the name suggests) methods. Similar to entity hydration in Doctrine, where you turn array to object.


**What could work, would be using other native dao methods**, since now is used only find(): https://github.com/Zenify/DoctrineMethodsHydrator/blob/master/src/Zenify/DoctrineMethodsHydrator/ParametersToEntitiesConvertor.php#L53

- findBy(array('slug' => $slug))

Maybe look at: https://github.com/Zenify/DoctrineMethodsHydrator/issues/1

That could be a way to go.