[REF] web: toggle new classes on grouped list views

Minor changes to allow better design.

addons/web/static/src/js/views/list/list_renderer.js

@@ -404,6 +404,8 @@ var ListRenderer = BasicRenderer.extend({
         }
         return $('<tr>')
                     .addClass('o_group_header')
+                    .toggleClass('o_group_open', group.isOpen)
+                    .toggleClass('o_group_has_content', group.count > 0)
                     .data('group', group)
                     .append($th)
                     .append($cells);

addons/web/static/src/less/list_view.less

@@ -35,14 +35,15 @@
     .o_column_sortable {
         .user-select(none);  // Prevent unwanted selection while sorting
 
-        &.o-sort-up:after {
+        &:after {
             font-family: FontAwesome;
             margin-left: 5px;
+        }
+
+        &.o-sort-up:after {
             content: "\f0d7";
         }
         &.o-sort-down:after {
-            font-family: FontAwesome;
-            margin-left: 5px;
             content: "\f0d8";
         }
     }