Forgot to commit one file

It's now possible to get notified on preference object changes in
UserStore

java/com.sap.sse.security/src/com/sap/sse/security/PreferenceObjectListener.java

@@ -0,0 +1,5 @@
+package com.sap.sse.security;
+
+public interface PreferenceObjectListener<PrefT> {
+    void preferenceObjectChanged(String username, String key, PrefT oldPreference, PrefT newPreference);
+}