Across the river, the Humvees are gone. The helicopters fewer. Sirens a rarity. The guns are back in the armory and the kids are once again at play in the street. Boston is getting back on track after last week’s bombing and the ensuing manhunt that terminated in a Watertown backyard. This weekend, Red Sox slugger David Ortiz helped bookend a tragic episode with his emphatic declaration of allegiance to the city and its people. Indeed, Boston is returning to “normal” even if we will never be the same.