[Routing] NamePrefix option for Route annotation

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       |  MIT
| Doc PR        | 

Added ability to set name prefix to routes through annotations. Example:

```php
/**
 * @Route("/", namePrefix="sf2_")
 */
class SomeController
{
    /**
     * @Route("/", name="test")
     * Name will be sf2_test
     */
    public function someAction()
    {
    }
}
```

This option must be used only in annotations for class!