Fix startup for db4o 8.0

The node previously wouldn't start up with db4o8.0, this commit fixes it.

The error message was:
NFO   | jvm 1    | 2013/01/03 13:54:42 | WrapperManager Error: Error in WrapperListener.start callback.  java.lang.NoSuchMethodError: com.db4o.ObjectContainer.get(Ljava/lang/Object;)Lcom/db4o/ObjectSet;
INFO   | jvm 1    | 2013/01/03 13:54:42 | WrapperManager Error: java.lang.NoSuchMethodError: com.db4o.ObjectContainer.get(Ljava/lang/Object;)Lcom/db4o/ObjectSet;
INFO   | jvm 1    | 2013/01/03 13:54:42 | WrapperManager Error:         at freenet.node.NodeCrypto.getNodeHandle(NodeCrypto.java:622)
INFO   | jvm 1    | 2013/01/03 13:54:42 | WrapperManager Error:         at freenet.node.Node.<init>(Node.java:1539)
INFO   | jvm 1    | 2013/01/03 13:54:42 | WrapperManager Error:         at freenet.node.NodeStarter.start(NodeStarter.java:196)
INFO   | jvm 1    | 2013/01/03 13:54:42 | WrapperManager Error:         at org.tanukisoftware.wrapper.WrapperManager$11.run(WrapperManager.java:2979)
INFO   | jvm 1    | 2013/01/03 13:54:43 | Shutting down...