COMMERCIAL AND MIXED USE DESIGN   The integration of differing building uses together calls for a careful blend of practical considerations such as accessibility and neighbourliness whilst the visual design balances continuity with distinctiveness.   Illustrated here are a Thames-side rowing club within a scheme of apartments, a newbuild supermarket on the edge of the historic town centre of Edenbridge, Kent and the emerging design for shops and sheltered housing at Bolnore Village.