Minor bug fixes for backup removal of old backup files and if restore finds no backups.

The TAR command for backing up wordpress had a typo which made it backup the wordpress db and files directories. Although it still worked there is no need to backup the db directory as it is restored with the import of the wordpress.sql file.

Added support to backup and restore multiple wordpress sites (jails).

You can now backup your wordpress install multiple time. The script defaults to 2 but that can be changed in the backup-config. When restoring it will give a list of backups with a date stamp to choose from.

The cron variable is not needed as the script will backup automatically if run from a cron task.
All config parameters are now optional and defaults are set in the script.
README.md Clarified

Script has been adjusted to minimize parameters in the backup-config.
Compatible with multiple wordpress sites.

Thanks to @Basil Hendroff for his suggestions.