Add script to export data to CSV

This can be imported by Libra for Android

export.php

+<?PHP
+
+ require('user-data.php');
+
+ /* For format of user-data.php see comment in data.php.
+  *
+  * In addition, this script requires a START_DATE constant containing
+  * the unix timestamp of the first entry in the $data array.
+  */
+
+ foreach ($data as $week => $value) {
+  if ($value != -1) {
+   echo date('Y-m-d', strtotime('+' . $week . ' weeks', START_DATE)), ';', $value, "\n";
+  }
+ }
+
+?>