Weekly backups need to be smarter

The weekly backup system right now is not impervious to table locking. If the backup happens while a recording is going, things can break pretty bad. Also, the user should be able to reconfigure the location the backup will occur via a debconf variable.

Quoted from #mythtv
<sphery> superm1: Sounds good. Might want to have your script check for current recording activity (i.e. using the XML status page or something) as table locking can cause issues for recordings.