Editor’s Note: The Sentinel sports staff is putting together a summer series looking at the legacies of the most influential African-American athletes in history. Today: Jackie Joyner-Kersee.The first lady of track and field.It’s the nickname that Jackie Joyner-Kersee was given after becoming the best female heptathlete in the world.Her mother, Mary Joyner, named her Jacqueline after Jaqueline Kennedy Onasis, John F. Kennedy’s wife. She hoped that one-day Joyner-Kersee would