rename 'label' to 'name'.

Warning : this commit require to rename some table column, but the
original Version file has been update.

If you do not care to loose your date, you may run :

```
php app/console doctrine:migrations:execute --down 20160318111334
php app/console doctrine:migrations:execute --up 20160318111334
php app/console doctrine:cache:metadata #(if you have a cache for
doctrine meta date)
```
close #20

Resources/views/Participation/edit.html.twig

@@ -13,7 +13,7 @@
             </tr>
             <tr>
                 <th>{{ 'Associated event'|trans }} </th>
-                <td>{{ participation.event.label }}</td>
+                <td>{{ participation.event.name }}</td>
             </tr>
             <tr>
                 <th>{{ 'Date'|trans }} </th>

Resources/views/Participation/new.html.twig

@@ -15,7 +15,7 @@
             </tr>
             <tr>
                 <th>{{ 'Associated event'|trans }} </th>
-                <td>{{ participation.event.label }}</td>
+                <td>{{ participation.event.name }}</td>
             </tr>
         </tbody>
     </table>