SAK-23251 Pass through the underlying object rather than converting to strings.

When converted to strings MySQL didn't work as it's didn't convert the prepared statement strings back to integers/datetimes and so the range selection didn't work.

git-svn-id: https://source.sakaiproject.org/svn/calendar/trunk@120528 66ffb92e-73f9-0310-93c1-f5514f145a0a