Add file.superseded column and interface

Untested.
Fix superseded evolutions.

Adding inherited columns is a mess.  Drop unused asset_duration view.
Merge remote-tracking branch 'github/master' into supersede
Add index on file.superseded
Add Asset.superseding and Asset.get cleanups
Add ingest.asset table to log ingested files
Change how db resets are done now that I've added another schema
Fix asset after removal of format join