Fixed list search

Using list search function, I searched for a recently added event, and
recently added film time:
- the new event is found, but always with associated date/time of
0000-00-00 00:00:00 (events created earlier have sensible date/times)
- the new film event is not found (at all)

renderer was using old dt_start and dt_end for rendering display.
Switched to start_date and end_date.  Adjusted event search callback to
also search for films events