Scheduled Task System

[euantorano]

A system to provide the running of scheduled tasks should be provided. Scheduled tasks should be used to perform actions such as role promotions, email reviews, sitemap generation, and more.

Features

• [x] Tasks should be ran upon a time based schedule.
• [x] Tasks should be implemented as classes extending a base MyBB\Core\Tasking\AbstractTask class.
• [x] Tasks should be able to be ran as a Cron job, or by using a background queue processor, or by using another in-page running mechanism.

[JN-Jones]

Just a note to whoever implements this: Old captchas need to be deleted too (https://github.com/mybb/mybb/blob/feature/inc/tasks/hourlycleanup.php#L44-L46)

[euantorano]

Moved to Alpha 2.