Long before Dr. Martin Luther King Jr. consecrated Grace Cathedral, Nob Hill was holy ground in the battle for justice for God's people.    KingPlus50 tours April 8, 15, 22 and 29 show the evolution of faith-based liberation theology and how it shaped King even as a teenager in the 1940s before anyone had heard of him.   Tours begin at the intersection of Leavenworth and California Streets. Oxford University Press historian John William Templeton, the bicentennial speaker for the birthday of Frederick Douglass at the African American Civil War Museum, leads an intimate tour through sites which shaped King including the role of Langston Hughes and Dr. Howard Thurman.