Searches for a field with given Name, returns it's index or -1 if not found.
function IndexOfExposedEvent(const EventName: string; out Event: TX3DEvent): Integer;
Returns if EventName is an event implicitly exposed by one of our exposed fields (i.e. set_xxx or xxx_changed). If yes, then returns index of event, and the event reference itself (so always Fields[ReturnedIndex].ExposedEvent[ReturnedEvent.InEvent] = ReturnedEvent). Otherwise, returns -1.