I have always been a great fan of composer Stephen Sondheim. But I must confess that his “Sweeney Todd: the Demon Barber of Fleet Street,” with book by Hugh Wheeler, currently being performed through Nov. 9 by the Porchlight Musical Theatre Company at Stage 773, 1525 W. Belmont Ave., has never been among my favorites. After all, what was there to like? A story of revenge, horrific murders, cannibalism — all done with a Satanic humorous twist. This is an opinion, I might add, that was shared with a …