Add a option to specify the request original name

I'm not sure this code is the way to go, I would thanks if someone enlighten me and point me an direction.

I want to be able do have:

URL?sent_date=XXXX

```php
/**
 * @Rest\QueryParam(
 *     name="sentDate",
 *     strict=true,
 *     nullable=false,
 * )
 * ...
 */
public function XXXAction($sentDate)
```

This case is just about underscore and camel case, but I also want to be able to decouple my URL query parameters names from the name of variable, eg:

I also want to be able to do stuff like:

URL?country=PT

public function XXXAction($countryCode)

At URL I don't need to country_code, because in all the API I just use country as the code, there is not other way to identify a country, but lower layers I can have: $country (the Country entity) $countryId (the ID of country on DB) and $countryCode, so I need my variable to be more specify.

With this code I add a option at Param annotation, so it can be done this:

```php
/**
 * @Rest\QueryParam(
 *     name="sentDate",
 *     requestName="sent_date",
 *     strict=true,
 *     nullable=false,
 * )
 * ...
 */
public function XXXAction($sentDate)
```

The requestName is optional if is not provided will fallback so no BC, I'm not sure about the name of the option.