Make get all notications return in csv format too:

* This adds functionality (via an extra req param) to the
* existing get all notifications method allowing us to specify
* when we want the API to return in csv/non-csv format

app/schemas.py

@@ -490,6 +490,7 @@ class NotificationsFilterSchema(ma.Schema):
     include_jobs = fields.Boolean(required=False)
     include_from_test_key = fields.Boolean(required=False)
     older_than = fields.UUID(required=False)
+    format_for_csv = fields.String()
 
     @pre_load
     def handle_multidict(self, in_data):