added changed event handler.

JString.h

@@ -69,6 +69,7 @@ namespace coreutils {
 
 	 Proxy& operator=(coreutils::MString value) {	    
 	    jstring.set(key, value);
+	    jstring.changed(key, value);
 	    return *this;
 	 }
 
@@ -84,6 +85,8 @@ namespace coreutils {
       JString & operator=(coreutils:: ZString value);
 
       MString pretty();
+
+      virtual void changed(ZString key, ZString value);
       
     private:
       void removeWhitespace();