SecurityForm: Add helptext

refs #6641

modules/monitoring/application/forms/Config/SecurityForm.php

@@ -27,7 +27,10 @@ class SecurityForm extends Form
             array(
                 'label'     =>  'Protected Custom Variables',
                 'required'  =>  true,
-                'value'     =>  $this->config->protected_customvars
+                'value'     =>  $this->config->protected_customvars,
+                'helptext'  =>  'Comma separated case insensitive list of protected custom variables.'
+                              . ' Use * as a placeholder for zero or more wildcard characters.'
+                              . ' Existance of those custom variables will be shown, but their values will be masked.'
             )
         );
         $this->setSubmitLabel('Save');