Photo by joekerstef. It starts off like so many routine crime stories: the Post reports this morning that Nathaniel R. Mines Jr., a councilman in Fairmount Heights, Maryland — just over the District’s eastern border in Prince George’s County — was arrested on the charge of impersonating a police officer. Fair enough. But in Fairmount Heights, it’s just the most recent incident in a long and tiring series of crimes which the townspeople of…