MCLEAN, Virginia, May 5 [Category: BizTravel] -- Hilton Worldwide Holdings posted the following news release: * * * DoubleTree by Hilton Unveils 'piebird,' Newest Dining Concept From StiR Creative Collective Celebrating the rich traditions of American cooking, the approachable American restaurant perfectly complements the brand's signature warm hospitality and caring service MCLEAN, Va. - Today, DoubleTree by Hilton announced an original restaurant and bar concept, piebird, which will begin  more