backup server support and incremental backups

[kilburn]

You should link to the source when you're slightly modifying an existant script from a website that nicely explains it's concepts, usage, and pitfalls.

Additionally, I don't think we're going to add any full server backup into ispcp. There are a myriad of readily available tools that you can easily install into your server and will better fit your needs (I use rsnapshot to get centralized rotating backups of all my servers, others use rdiff-backup, etc.).