A Calling of Faith and Art in a Russian Church
Rev Andrei Davydov is using his art to finance restoration of 12th century church in Pskov, one of oldest cities in all Russia; Cathedral of the Nativity of St John the Baptist, which dates to 1124, was in shambles when Russian Orthodox patriarchate regained it in 1991; Rev Davydov, who has worldwide reputation for his painted icons, now accepts commissions from other churches to pay for his church's repairs and rebuilding; photos; map (M)