Missing CAMEO codes for 2017 events

[andybega]

The 2017 events file is missing a "CAMEO column", but it does have "Event Text".

1. Fix for future reads: there already is a file-specific non-standard treatment for dates in read_events_tsv(), so maybe just add another fix fo this there.
2. Fix for DB if already ingested: if the file has already been ingested into the database, those records will require an update to add in the missing CAMEO codes.