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.
Thx, for your comment. You are probably right, that my solution is too magic. To use findBy solves just one my problem. 

Second problem is, when I want array of objects according to some parameters. You are right, I will probably need some limit, offset, ... so I have to for this feature get instance of class, when I can implement it .

I'm not sure, If you are against this feature or you just don't like my implementation.

I understand this extension as syntactic sugar, where I don't need call em or my dao method and I get entity. It give me sense to have array of entities... :-)