Add 'items' as reverse relatiob from Term to Item

This was defaulting to message_set, and we're still thinking we might
rename Message to Item at some point

django/website/data_layer/migrations/0004_auto_20150720_1723.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('data_layer', '0003_message_terms'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='message',
+            name='terms',
+            field=models.ManyToManyField(related_name='items', to='taxonomies.Term'),
+        ),
+    ]

django/website/data_layer/models.py

@@ -12,7 +12,7 @@ class DataLayerModel(models.Model):
 class Message(DataLayerModel):
     body = models.TextField()
     timestamp = models.DateTimeField(null=True)
-    terms = models.ManyToManyField(Term)
+    terms = models.ManyToManyField(Term, related_name="items")
 
     def apply_term(self, term):
         # TODO: test this