Edits to local backup script.

wattdepot_backup_script.sh
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* The **version number** and **pg_dump** location are now variables
* The user home directory is now a variable
* If there are no backups to delete, the script ends without trying to list the backups to delete again

wattdepot_postgresql_backup_procedure.txt
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* Database backup verification instructions now ask the user to check that the last sensor data taken is close to the time at which the backup was made, instead of having them check the SPA page.
* Documentation now mentions need to do chmod +x on scripts before running them in a cron job