Remove unused overdue invoice setting move master cron switch out of notificaiton and into cron

admin/database_updates/2.6.6.php

@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * ITFlow - Database update to version 2.6.6 (from 2.6.5)
+ * Included by admin/database_updates.php - do not access directly
+ */
+
+defined('FROM_DB_UPDATER') || die("Direct file access is not allowed");
+
+    // config_invoice_overdue_reminders never did anything. Both setup paths seeded it with
+    // '1,3,7' and two files read it, but the only line that would have used it was commented
+    // out in the nightly job - the reminder schedule is a hardcoded array. The read in
+    // includes/load_global_settings.php also ran intval() over a comma-separated string, so
+    // the global was 1 whatever the column said.
+    //
+    // Nothing in the app has ever written to it either, so no install has a value worth
+    // keeping and there is nothing to migrate anywhere.
+
+    mysqli_query($mysqli, "ALTER TABLE `settings` DROP COLUMN IF EXISTS `config_invoice_overdue_reminders`");