This class can be used to perform several site maintenance tasks. Currently it can: - Take backups of database tables to compressed XML files - Rotate backup files deleting files older than a given number of days - Remove files from given directories that match certain name patterns or were modified for the last time some time ago - Delete obsolete records from certain database tables - Check and optimize MySQL database tables - Calculate space occupied by site files and data in MySQL tables - Estimate the number of days before the site files exceed a given disk space limit