By Michele Nyberg MEMPHIS, TN — Civil rights leaders, clergy, union members and community activists on Tuesday advocated a $15 minimum wage while commemorating the 49th anniversary of the Rev. Dr. Martin Luther King’s assassination. “In this country, 52 percent of African Americans make less than a living wage,” said the Rev. William Barber, president of the NAACP in North Carolina. “We have 6 million people in this country whose only income is food stamps.” Tuesday’s memorial activities culminated in a march from City Hall to the Lorraine Motel, now the National Civil Rights Museum, where religious services were held…