The Maine Army National Guard reopened the Readiness Center in Calais in November 2016. Photo courtesy Maine National Guard.CALAIS — The Maine National Guard has submitted a proposal to the Office of the Maine Attorney General to sell the Calais armory, a step that could advance the city’s long‑standing effort to buy the building. Lt. Col. Margaret St. Pierre, the Guard’s public affairs officer, confirmed the proposal to Monitor Local and said t…