Improved settings of CSPs.

Added manifest.json.
Added further security-related HTTP headers.

edit/users.php

@@ -84,7 +84,7 @@ if (isset($task) and $task == "insert") { // Adding new users.
  * Output
  */
 
-echo printBackendHead($translations['start'], $translations['start'], $settings['logo']);
+echo printBackendHead($settings, $translations['start'], $translations['start'], $settings['logo']);
 echo printBackendHeader($translations['usersOverview'], $translations['helpUsers']);
 
 echo '