Add link between corporation and its parent

stages/migrations/0006_corporation_parent.py

@@ -0,0 +1,19 @@
+# Generated by Django 1.9.1 on 2016-01-18 12:23
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stages', '0005_extended_contact_email'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='corporation',
+            name='parent',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL,
+                to='stages.Corporation', verbose_name='Institution mère'),
+        ),
+    ]