Include reference in OTU projection
From @Miminko in #969:

> Websocket messages detailing OTU insert & update requires a reference field indicating which reference id the particular otu is associated with.
diff --git a/virtool/db/otus.py b/virtool/db/otus.py
index 81d702222..0f8bd9d40 100644
--- a/virtool/db/otus.py
+++ b/virtool/db/otus.py
@@ -10,10 +10,11 @@ from virtool.api.utils import compose_regex_query, paginate
 
 PROJECTION = [
     "_id",
-    "name",
     "abbreviation",
-    "version",
-    "verified"
+    "name",
+    "reference",
+    "verified",
+    "version"
 ]
 
 SEQUENCE_PROJECTION = [
['virtool/db/otus.py']