include more detail for system backups in the backup logs

I would like to add a request for more detail in the system backups section of the backup logs. Now that we'll have timestamps, lines simply say "starting|ending backup of [file|dir]" would be great.

Like:

timestamp: starting backup of /var/lib/mysql

timestamp: completed backup of /var/lib/mysql

This would allow me to determine if resource usage (load and i/o) spikes regularly occur during specific sections of the backup process and greatly speed up detecting the root cause of backup issues that occur during this part of the backup.