Event Search Filter Update: Category Path

When searching for an event type, it's useful to use the existing closure/event categories to narrow your search for the type of event you're looking for. An improvement for this search filter would be to make the sub-type selection optional, so the user can choose to be either very specific (current state) or less specific in their search. This is especially helpful if the operators do not consistently use the same closure sub-categories, or if you're interested in all events with the same top-level category regardless of the sub-type.