Old itemIdentifier function
func itemIdentifier<T: IQModelableCell>(_ type: T.Type, of model: T.Model,
comparator: (T.Model, T.Model) -> Bool) -> IQItem?New itemIdentifier function makes it easy to find an item by removing some arguments from the function
func itemIdentifier<T: IQModelableCell>(of type: T.Type, where predicate: (T.Model) -> Bool) -> IQItem?