Ever since it opened on Broadway in 1975 and won nine Tony Awards, “A Chorus Line” has always been and continues to be my all-time favorite musical.I love the music by Marvin Hamlisch, the lyrics by Edward Kleban and certainly the concept, original direction and choreography by Michael Bennett.Porchlight Music Theatre, known for its excellent restorations of some of the great musicals of the past, including “Pal Joey,” “Sweeney Todd,” “Memphis” and “Gypsy,” is now …