CENTENNIAL, Colo.—A former Nevada prison inmate was sentenced Tuesday to three consecutive life sentences in the long-unsolved 1984 hammer killings of three Colorado family members, including a 7-year-old girl, inside their suburban Denver home. Sixty-one-year-old Alex Ewing was convicted Aug. 6 of first-degree murder after a two-day trial in which prosecutors contended Ewing used a…