* Create DuplicateLogReference
* Set and clear duplicate log references
* Export duplicate_log_reference_id for lettings
* Export duplicate_log_reference_id for sales
* Export duplicate_log_reference_id in xml
* Update tests
* Update existing duplicate log references
* Rename a field
* Add missing sales deduplication steps
* Set duplicate_set_id straight on logs
* Do not update updated_at to prevent export
* Increment duplicate_set_id
* Update duplicates when they change sets
* Remove duplicates when deleting logs
* correctly update duplicate set IDs when answer is changed through normal form flow