The most important item in Kenneth “Kenny” Powell III’s Clayton office isn’t a legal brief, a settlement agreement or a framed award. It’s a photograph. The photo features Powell’s great-great-great-grandfather, an enslaved man from South Carolina, and his 10 children. The generations that followed included a blacksmith and preacher, a World War I veteran and Jerome Williams Sr., a St. Louis physician and civil rights leader. Two of Williams’ so…