Charles Krantz — Chuck, to his friends — makes his way along Boylston Street dressed in the armor of accountancy: gray suit, white shirt, blue tie. His black Samuel Windsor shoes are inexpensive but sturdy. His briefcase swings by his side. He takes no notice of the chattering after-work throngs eddying around him. He’s in Boston attending a week-long conference titled Banking in the Twenty-First Century. He has been sent by his bank, Midwest Trust, all expenses paid. Very nice,