Reset demo site weekly

[josecelano]

Relates to: torrust/torrust-index-gui#614

Build a small script to reset the demo site every week. It can be executed as a cron job.

If we want, we can seed the reset site with some torrents by using the Index seeder. We can create a new one to upload some torrents from a folder or something like that if we don't want to use boring sequential torrents.

cc @da2ce7 @cgbosse

[josecelano]

@cgbosse suggested keeping it as it is.