implement model changes

- add new domains.apps.AppConfig to allow translatable app description for
  domains app
- link domains to a customer
- extract common functionality from domains.models.MailDomain into abstract
  domains.models.DomainBase
- add separate domains.models.HostingDomain to allow for generic external
  domains
- add new hostingpackages.models.CustomerHostingPackageDomain to assign hosting
  domains to hosting packages

gnuviechadmin/hostingpackages/migrations/0004_customerhostingpackagedomain.py

@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+import django.utils.timezone
+import model_utils.fields
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('domains', '0002_auto_20150124_1909'),
+        ('hostingpackages', '0003_auto_20150118_1407'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='CustomerHostingPackageDomain',
+            fields=[
+                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
+                ('created', model_utils.fields.AutoCreatedField(default=django.utils.timezone.now, verbose_name='created', editable=False)),
+                ('modified', model_utils.fields.AutoLastModifiedField(default=django.utils.timezone.now, verbose_name='modified', editable=False)),
+                ('domain', models.OneToOneField(verbose_name='hosting domain', to='domains.HostingDomain')),
+                ('hosting_package', models.ForeignKey(related_name='domains', verbose_name='hosting package', to='hostingpackages.CustomerHostingPackage')),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=(models.Model,),
+        ),
+    ]