Improve memory useage about databackup

[jgulledge19]

Improved memory usage in large DBs buy dumping in memory strings to temp files then rebuilding temp files into sql files. PHP seems to consume a lot more memory than the string on very large loop concatenation than the actual size of the string. I now am backing up 275mb DB with about 490mb peak usage in PHP. It may be possible to further reduce memory usage in PHP.