Change log date export format

[froboy]

Current behavior:
The time exported in Log Archives by openy_gc_logs is in Unix time, which isn't easy for users to use in spreadsheets or other data (although I did find a nice formula for converting (=(A1/86400)+DATE(1970,1,1)).

created,event_type,entity_type,entity_bundle,entity_id
1602008775,entityView,node,gc_video,23

Expected behavior:
Exported logs should have the time in some format that's easily recognizable by spreadsheets and humans alike.

[froboy]

This will be covered in https://trello.com/c/qr5lGzd0/35-user-activity-log-v2-score-5

[froboy]

fivejars#152 resolves this.