Dashboard: store graph data in file instead of cookie

This prevents the creation of too large cookies.

plugins/dynamix/include/InitCharts.php

@@ -0,0 +1,25 @@
+<?PHP
+/* Copyright 2005-2022, Lime Technology
+ * Copyright 2012-2022, Bergware International.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ */
+?>
+<?
+$docroot = $docroot ?? $_SERVER['DOCUMENT_ROOT'] ?: '/usr/local/emhttp';
+$charts  = '/var/tmp/charts_data.tmp';
+
+switch ($_POST['cmd']) {
+case 'get':
+  echo @file_get_contents($charts) ?: '{"cpu":"","rxd":"","txd":""}';
+  break;
+case 'set':
+  file_put_contents($charts,$_POST['data']);
+  break;
+}
+?>