FilesystemFileHandler seems to do too much

[rjkip]

As originally submitted by @DRvanR:

At this point it acts both as a FileHandler, and a FileHandler-that-lets-you-make-backups, where backups are only made if the source file exists.

Seems that splitting the backup strategy from the FilesystemFileHandler would make both things less complex and would provide two objects with a better, single, purpose.