‘Itzhak’ shows how even a violin whiz can crack wise

“When I hear that playing, it’s like breathing. It’s like being alive.”That’s Toby Perlman, the wife of Itzhak Perlman, describing the music of her husband in the documentary “Itzhak.” Director Alison Chernick profiles the violin virtuoso, through his performance, of course, but she also reveals a personality as expressive as his musicianship.We are introduced to the film’s subject not in a concert hall, but at Citi Field in Queens, N.Y., where the