Improved documentation.

h2/src/main/org/h2/tools/Recover.java

@@ -95,6 +95,7 @@ public class Recover extends Tool implements DataHandler {
      * <tr><td>[-trace]</td>
      * <td>Print additional trace information</td></tr>
      * </table>
+     * Encrypted databases need to be decrypted first.
      * @h2.resource
      *
      * @param args the command line arguments