move untested extensions to the archive folder (see comment)

anyone wishing to test and confirm it should go back to the project can submit an issue (or better propose a PR).

archive/untested-extensions/ext-server_opensave/savefile.php

@@ -0,0 +1,16 @@
+<?php
+  // You must first create a file "savefile_config.php" in this extensions directory and do whatever
+  //   checking of user credentials, etc. that you wish; otherwise anyone will be able to post SVG
+  //   files to your server which may cause disk space or possibly security problems
+  require('savefile_config.php');
+  if (!isset($_POST['output_svg'])) {
+    print 'You must supply output_svg';
+    exit;
+  }
+  $svg = $_POST['output_svg'];
+  $filename = (isset($_POST['filename']) && !empty($_POST['filename']) ? preg_replace('@[\\\\/:*?"<>|]@u', '_', $_POST['filename']) : 'saved') . '.svg'; // These characters are indicated as prohibited by Windows
+
+  $fh = fopen($filename, 'w') or die("Can't open file");
+  fwrite($fh, $svg);
+  fclose($fh);
+?>