In these busy times for the art world, it sometimes seems as though every museum in the country is either looking for a new director or engaged in a major building project. The Parrish Art Museum in Southampton is doing both. Its director of 26 years, Trudy Kramer, will retire at the end of the year, just as the museum breaks ground on a new 45,000-square-foot facility designed by the Swiss architectural firm Herzog & de Meuron.