skip duplicate rows

[jameslaneconkling]

if downloader is run multiple times, it will reject any csv file upload if that file already matches rows in the db. GLOBALEVENTID has a PRIMARY KEY constraint that will throw a error: duplicate key value violates unique constraint error.

only an issue if downloader is run for the same dates multiple times with different filters. would be nice to ignore duplicates and let any new rows through, i.e. something like UPSERT.