Upgrade to Django 1.11

- Deprecation warnings using Django 1.8 are resolved.
- Deprecation warnings using Django 1.11 are resolved.

- Admin: grappelli is no longer used.
- Upgrade to django-autocomplete-light v3 (v2 is not 1.11 compatible).
  * autocomplete.modelform_factory being dropped, code uses dal Select2
    views and widgets.

bda/migrations/0009_revente.py

@@ -47,12 +47,14 @@ class Migration(migrations.Migration):
             model_name='spectaclerevente',
             name='attribution',
             field=models.OneToOneField(to='bda.Attribution',
+                                       on_delete=models.CASCADE,
                                        related_name='revente'),
         ),
         migrations.AddField(
             model_name='spectaclerevente',
             name='seller',
             field=models.ForeignKey(to='bda.Participant',
+                                    on_delete=models.CASCADE,
                                     verbose_name='Vendeur',
                                     related_name='original_shows'),
         ),
@@ -60,6 +62,7 @@ class Migration(migrations.Migration):
             model_name='spectaclerevente',
             name='soldTo',
             field=models.ForeignKey(to='bda.Participant',
+                                    on_delete=models.CASCADE,
                                     verbose_name='Vendue à', null=True,
                                     blank=True),
         ),