/**
  * Sends an e-mail (text format) from the system to the specified recipient. 
  * Difference to sendSystemEmail(): Content is extracted from a template file.
  * 
  * @param WebSoccer $websoccer current context.
  * @param I18n $i18n messages context
  * @param string $recipient recipient e-mail address
  * @param string $subject Already translated e-mail subject.
  * @param string $templateName name of template (NOT template file name, i.e. WITHOUT file extension!) to use for the e-mail body.
  * @param array $parameters array of parameters to use in the template (key=parameter name, value= parameter value).
  */
 public static function sendSystemEmailFromTemplate(WebSoccer $websoccer, I18n $i18n, $recipient, $subject, $templateName, $parameters)
 {
     $emailTemplateEngine = new TemplateEngine($websoccer, $i18n, null);
     $template = $emailTemplateEngine->loadTemplate('emails/' . $templateName);
     $content = $template->render($parameters);
     self::sendSystemEmail($websoccer, $recipient, $subject, $content);
 }