find_one() parses ObjectId() if auth_username_field='_id'
Merge branch 'auth_username_field_id' of https://github.com/bcattle/eve into bcattle-auth_username_field_id
Allow 'auth_username_field' to be set to 'ID_FIELD'.
Bryan Cattle
Merge branch 'bcattle-auth_username_field_id' into develop