NEW YORK (Reuters) - Michelle Obama will be ceding the title of first lady to Melania Trump next month, but she may hold for some time the other distinction she earned during her time in the White House: America's best known advocate for healthy food. The non-profit organization she helped create as first lady, Partnership for a Healthier America (PHA), where she is honorary chair, will continue its work convincing food companies to improve nutrition content and labeling of products, the group said. "Michelle Obama has been a tremendous leader in this space," said Larry Soler, president and chief executive...