If you go to GALA Hispanic Theatre to see Lope de Vega’s “El Caballero de Olmedo” (“The Knight from Olmedo”), you may think you’ve stumbled into the wrong theater. “El Caballero,” a stirring drama of love, honor and valor from Spain’s Golden Age, conjures up images of elaborate rooms, painted ceilings, the highly embellished arts that were celebrated in Spain during the 17th century.