Backup

The backup process needs a revision:

1. The log does only include the latest backup reference. It's more a status file right now but not a log file
2. ZipBackup should allow to control `$ignorePaths`and `$ignoreFolders` and maybe the timeout setting, e.g. from the site configuration panel
3. The folderToZip function should add an empty folder for all folders listed in `$ignoreFolders` or you should think about a third array, e.g. `$addAsEmptyFolders`.

The second point is important, not only for a pro version. Right now the backup process can produce what I would call a "silent bug". The process does not terminate, the working indicator spins forever and the backup folder contains a process file which may consume hundreds of MB with a .zip.a233434 something extension. Adding some extra folders in code to the `$ignoreFolders` I was able to solve this.

Regards.
uh