Billy and Sheila Canaan just wanted out of Baton Rouge. They didn''t expect to be bit players in a new movement to keep the Great Plains from emptying. Billy gave up a $90,000-a-year deputy sheriff's job for one that pays a third as much. Sheila kept slipping on the thick ice of a bitter Kansas winter and broke a rib. Son Clayton reluctantly started his senior year at a new high school. To their Cajun palates, Midwest cooking had all the zing of roasted cardboard. (Clayton keeps hot sauce in his locker.) So why Kansas, when other rural states offer...