better snapshots

Closes #114

Scripts updated:
* backupDiscover.py
* backupSnapshot.py
* pruneIndexes.py
* rotateIndexes.py

They all use cron/backup.conf for configuration
I'd like to leave the default to look for a .conf file the same name as the prog. We can tell it to use a consolidated .conf file in the .sh script the cronjob runs.