Incorrect default order for dataset items

[peichins]

When requesting a list of dataset items without specifying the order, the default order should be by the "order" column, but instead it is sorted by audio_recording_id then order.

In other words, requesting /datasets/$dataset_id/items/ incorrectly returns the same results as

select * from dataset_items
where dataset_id = $dataset_id
order by "audio_recording_id", "order"