Lana Del Rey is trading in “Summertime Sadness” for “Fiancé Fall” … as the singer looks set to marry her boyfriend, Jeremy Dufrene. According to the Lafourche Parish Clerk of Court … Lana stopped by with her boat captain beau Monday and picked up a marriage license. We’re told the marriage license has yet to be returned and recorded in the records … so, it seems Lana and Jeremy haven’t exchanged their vows — though,...