Ckeditor - Allow to use "class" attribute inside divs and spans.

In order to set glossary class. See BT#8968

main/template/default/javascript/editor/ckeditor/config_js.tpl

@@ -1,3 +1,5 @@
+/* Ckeditor global configuration file */
+
 CKEDITOR.editorConfig = function( config ) {
     // Define changes to default configuration here.
     // For complete reference see:
@@ -17,5 +19,8 @@ CKEDITOR.editorConfig = function( config ) {
         '{{ _p.web_main ~ 'inc/lib/elfinder/templates.php'}}'
     ];
 
+    // Allows to use "class" attribute inside divs and spans.
+    config.allowedContent = true;
+
     config.customConfig = '{{ _p.web_main ~ 'inc/lib/javascript/ckeditor/config_js.php'}}';
 };