Allowing translations to be easily extracted

When extracting Core or Web bundles translations, we always face this exception : 
 
```
   [Doctrine\Common\Annotations\AnnotationException]                                                                                                        
   [Semantical Error] The annotation "@Given" in method Behat\MinkExtension\Context \MinkContext::iAmOnHomepage() was never imported. Did you maybe forget to add a "use" statement for this annotation? 
```

As explained by everzet himself here  https://github.com/Behat/MinkBundle/issues/29 this PR resolves, the problem.