Significant fixes.

- An event `boardtools.cronstatus.modify_cron_task` was edited: `new_task_date` variable was added.
- The function for working with task dates was moved to the `listener.php`.

Fixes:
- Cron Task Notice now should work properly: it uses the same function as the Cron Status page.
- A JavaScript fix (after the last update for noscript compatibility).
- Version_helper updated fix.

The code was simplified and structured so now it is more readable.