“Manchester by the Sea” is a love story, a dark comedy and a requiem. Written and directed by Kenneth Lonergan, the movie follows Lee Chandler (Casey Affleck), who has moved from the fishing town where he was raised to the Boston suburb of Quincy (think Berwyn), where he works as a janitor and lives in the basement room of one of the apartment buildings he services.Lee is conscious stricken over his conduct in the titular town. He can’t beat his demons.He has to face them anyway, when he returns to …