Bulk create returns the created objects in the same order as they have been added.
In Postgres, the query was wrong, because ordering was not guaranteed.
When uploading datasets, the code uses a `bulk_create` to upload
Examples and Labels. It then filters the data from the database
based on when it was created. However, [Django doesn't enforce
the list order when calling filter](https://stackoverflow.com/questions/7163640/what-is-the-default-order-of-a-list-returned-from-a-django-filter-call)
unless ordering is specified. The previous behavior mismatched labels
and examples. When this was shown in the UI, the data would show labels
for incorrect examples (i.e. a label for message #2 would be shown on
message #1). This fix enforces that the data is returned in the order
it was inserted so that the data, label pair is as expected.