Add notification_type to notification table.

It seems like an oversight not to include the notification type in the notifcation.
When updating statistics a query to the template table is required to get the type, this update will mean that query does not have to happen.

migrations/versions/0035_notification_type_.py

@@ -0,0 +1,26 @@
+"""empty message
+
+Revision ID: 0035_notification_type
+Revises: 0034_pwd_changed_at_not_null
+Create Date: 2016-06-29 10:48:55.955317
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '0035_notification_type'
+down_revision = '0034_pwd_changed_at_not_null'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    op.add_column('notifications', sa.Column('notification_type', sa.String(), nullable=True))
+    op.execute('update notifications set notification_type = (select distinct(template_type) '
+               'from templates where templates.id = notifications.template_id)')
+    op.alter_column('notifications', 'notification_type', nullable=False)
+
+def downgrade():
+    ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('notifications', 'notification_type')
+    ### end Alembic commands ###