to_datetime: only convert datetime.date objects.

When d is of type datetime.datetime isinstance(d, datetime.date)
returns True.
get_time_points must return valid traffic times.
Let sponsors safely terminate a live campaign.

This will set the campaign's end_date to now so all traffic and
billing information is retained.
Add override to prevent setting promoted links over_18.
Only sponsors can unmarknsfw on promoted links.