add closed tasks

- the entity has a new column / property "closed" (boolean)
- An event listener in created during container compilation, which listen on tasks
  status changed
- The taskworkflow manager and task workflow definition indicate if the tasks is closed ;
- Add list for closed tasks in controller, and change parameter 'date_status' to 'status';
- and change query to allow to filter on closed tasks

Workflow/Definition/DefaultTaskDefinition.php

@@ -53,7 +53,7 @@ class DefaultTaskDefinition implements \Chill\TaskBundle\Workflow\TaskWorkflowDe
             && $task->getType() === 'task_default';
     }
     
-    public function getAssociatedWorkflowName()
+    public static function getAssociatedWorkflowName()
     {
         return 'task_default';
     }
@@ -89,4 +89,10 @@ class DefaultTaskDefinition implements \Chill\TaskBundle\Workflow\TaskWorkflowDe
         
         return self::TRANSITION_METADATA[$transition->getName()][$key];
     }
+    
+    public function isClosed(AbstractTask $task) 
+    {
+        return \array_key_exists('closed', $task->getCurrentStates())
+            || \array_key_exists('canceled', $task->getCurrentStates());
+    }
 }