refix string error translation

app/Resources/translations/validators.en.yml

     name:
       notblank:          You must enter a name.
       toshort:           The name is too short.
+      toshort|error.element.name.toshort: The name is too short.
       tolong:            The name is too long.
+      tolong|error.element.name.tolong: The name is too long.
   url:
     invalid:             The URL is not a valid one.
   

app/Resources/translations/validators.fr.yml

     name:
       notblank:          Vous devez saisir un nom
       toshort:           Le nom est trop court
+      toshort|error.element.name.toshort: Le nom est trop court
       tolong:            Le nom est trop long
+      tolong|error.element.name.tolong: Le nom est trop long
   url:
     invalid:             L'adresse fournie est invalide
   

src/Muzich/CoreBundle/Entity/Element.php

    * 
    * @ORM\Column(type = "string", length = 128)
    * @Assert\NotBlank(message = "error.element.name.notblank")
-   * @Assert\Length(min = 3, max = 84, minMessage = "error.element.name.toshort", maxMessage = "error.element.name.tolong")
+   * @Assert\Length(min = 3, max = 84, minMessage = "error.element.name.toshort|error.element.name.toshort", maxMessage = "error.element.name.tolong|error.element.name.tolong")
    * @var type string
    */
   protected $name;