Adding some early Notifications stubs

* A basic NotificationTemplate model class with early notification type
  definitions
* Initial implementations of the Email, Slack, and Twilio Notification
  backends using the Django email backend system
* Some dependencies thereof

awx/main/models/notifications.py

@@ -0,0 +1,37 @@
+# Copyright (c) 2016 Ansible, Inc.
+# All Rights Reserved.
+
+import logging
+
+from django.db import models
+from awx.main.models.base import * # noqa
+from awx.main.notifications.email_backend import CustomEmailBackend
+from awx.main.notifications.slack_backend import SlackBackend
+from awx.main.notifications.twilio_backend import TwilioBackend
+
+# Django-JSONField
+from jsonfield import JSONField
+
+logger = logging.getLogger('awx.main.models.notifications')
+
+class NotificationTemplate(CommonModel):
+
+    NOTIFICATION_TYPES = [('email', _('Email'), CustomEmailBackend),
+                          ('slack', _('Slack'), SlackBackend),
+                          ('twilio', _('Twilio'), TwilioBackend)]
+    NOTIFICATION_TYPE_CHOICES = [(x[0], x[1]) for x in NOTIFICATION_TYPES]
+    CLASS_FOR_NOTIFICATION_TYPE = dict([(x[0], x[2]) for x in NOTIFICATION_TYPES])
+
+    class Meta:
+        app_label = 'main'
+
+    notification_type = models.CharField(
+        max_length = 32,
+        choices=NOTIFICATION_TYPE_CHOICES,
+    )
+
+    notification_configuration = JSONField(blank=False)
+
+    @property
+    def notification_class(self):
+        return CLASS_FOR_NOTIFICATION_TYPE[self.notification_type]