Event - Find Participants does not return any results when a price set is used

When using a price set for an event, all selected items are stored in civicrm_participant.fee_level. CRM/Event/BAO/Query.php looks for an exact match.

For example, if your event has multiple price set items and one is a meal choice for "Tuna Salad", when searching for participants that ordered the Tuna Salad, no participants are found.

The attached patch changed the query to wildcard the search term in the query.

(This was reported to Dave Greenberg at the CiviCamp in Washington, DC.)