CRM-15698 participant listing report: doesn't display all price fee options if values are identical in different sets

In the participant listing report, we have the option of filtering by the Fee Level field. This returns participants who have any of the selected options in their registration line items.

The query that pulls the list of available options for that filter groups by the field label. This is problematic, as you may have multiple price sets that have fields with the same label. The resulting query will consequently only pull registrants from one of the sets.

I think we should modify the query so that we display all values, and append the price set title so that the fee options can be distinguished easily.