MAPG-231 introduce unlisted maps

public/static/css/maps.css

@@ -13,6 +13,10 @@ div.mapItem.new {
     align-items: center;
 }
 
+div.mapItem.unlisted {
+    opacity: 0.6;
+}
+
 div.mapItem>div.title {
     background-color: #28a745;
     color: white;