Backup Rake Task to optionally include Human Readable Time

Description

Timestamps shown with ls -l is the only way to see the human readable time for when a backup was created. This is specifically annoying when a user wants to plan to move backups to a different location and they do not know if the timestamp will be updated.

Proposal

Currently backups look like this: 1477317140_gitlab_backup.tar

Could a flag be added to the backup rake task to include Human Readable Time with the Epoch time like this: 1477317140_oct_24_gitlab_backup.tar

Links / references

https://docs.gitlab.com/ce/raketasks/backup_restore.html#create-a-backup-of-the-gitlab-system

/cc @DouweM