remove unused hidden-settings; correct setting-language-strings-layout; add blacklist for usernames when creating a Customer which may lead to internal issues

Signed-off-by: Michael Kaufmann <d00p@froxlor.org>

lib/Froxlor/PhpHelper.php

@@ -416,6 +416,7 @@ class PhpHelper
 			'mysql_unprivileged_pass',
 			'admin_pass',
 			'admin_pass_confirm',
+			'panel_password_special_char',
 		];
 		if (!empty($global)) {
 			$tmp = $global;