Use result index instead of name.

For whatever reason name is not working. But we only get back one value, so we
can just get it by index (which used SQL's 1-based indexing, whee!).

src/main/java/com/samskivert/jdbc/jora/Table.java

@@ -244,7 +244,7 @@ public class Table<T>
         ResultSet rs = insertStmt.getGeneratedKeys();
         Object rawKey = null;
         if (rs.next()) {
-            rawKey = rs.getObject(primaryKeys[0]);
+            rawKey = rs.getObject(1);
         }
         @SuppressWarnings("unchecked")
         K key = (K)rawKey;