Migrate project owner to owners list

Issue #719
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/migrations/0038_auto_20150810_1354.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+def fill_in_owners(apps, schema_editor):
+    Project = apps.get_model('trans', 'Project')
+
+    for project in Project.objects.all():
+        if project.owner:
+            project.owners.add(project.owner)
+
+
+def fill_in_owner(apps, schema_editor):
+    Project = apps.get_model('trans', 'Project')
+
+    for project in Project.objects.all():
+        if project.owners.exists():
+            project.owner = project.owners.all()[0]
+            project.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('trans', '0037_auto_20150810_1348'),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            fill_in_owners,
+            reverse_code=fill_in_owner,
+        ),
+    ]