PEAT MARWICK AND NOLAN NORTON TO MERGE <Peat Marwick>, an accounting and management consulting firm, and <Nolan, Norton and Co>, an information and technology planning concern, said they have merged. The companies said with the merger Nolan now will be known as Nolan, Norton and Co-partners, the information technology arm of Peat Marwick. Also as part of the merger, Nolan's 21 principals have become Peat Marwick partners, the companies said.