#713 Backup at user-defined interval

[themint100]

I think it would be great if I could set a default
backup interval (e.g. weekly, monthly, whatever) that
would automatically do a backup for me (using the
current mechanism would be fine).

I suppose this would also require a config parameter
such as max. number of backups to keep.

I saw that there had been some earlier discussion of
max. number of backups, but not of the automatic backup
on interval aspect.

Thanks in advance!

-Greg