[gmap3]: allow subclasses to customize InfoWindow initialization (#1140)

Author: vrozkovec

gmap3-parent/gmap3/src/main/java/org/wicketstuff/gmap/api/GInfoWindow.java

@@ -101,9 +101,20 @@ public String getJSconstructor()
             args.set("zIndex", zIndex.toString());
         }
 
+        configureJSconstructor(args);
+        
         Constructor constructor = new Constructor("google.maps.InfoWindow").add(args.toJS());
         return constructor.toJS();
     }
+    
+    /**
+     * Allow subclasses to customize InfoWindow initialization.
+     * 
+     * @param args
+     */
+    protected void configureJSconstructor(ObjectLiteral args) 
+    {
+    }
 
     /**
      * Update state from a request to an AJAX target.