STATEN ISLAND, N.Y. — The St. Joseph by-the-Sea High School campus served as the backdrop Saturday for the school’s 2017 commencement ceremony. Proud parents and school faculty warmly greeted the 286 graduating. MANCHESTER — Denis Mailloux, the long-serving principal of Trinity High School, will ease out of that job beginning Jan. 1 and take over the full-time leadership of St. Joseph Regional Junior High School at the end of this…