Add sensible ordering to items

Improve experience when adding a new item lease in admin.

hardware_provisioning/models.py

@@ -112,6 +112,7 @@ class Item(models.Model):
 
     class Meta:
         verbose_name = 'objet'
+        ordering = ['designation', 'mac_address', 'serial']
 
     def give_back(self, storage=None):
         self.storage = storage