schemas/vegbien.sql: *_update_ancestors(): Made trigger deferred, so that it would run after all rows have been inserted in a bulk insert, such as during column-based import. This ensures that ancestors lists are not populated until all parents are inserted, which may occur out of order for datasources (such as NCBI) whose nodes are not in dependency order. (A node that newly acquires a parent will have to update all its descendants, which will then be updated again when its parent acquires its own parent.)