grantnav: Update cron snapshots to use '.' and `date` remove month
grantnav: Update cron snapshots to use '.' and `date` remove month

The cron jobs were not executing correctly due to the interpreter being
set to /bin/sh (dash) and therefore not having `source` available to
setup the python env.

Also improve the index names for the backups to contain the date they
were created

Also remove redundant month: */1 from monthly snapshot.

Fixes https://github.com/OpenDataServices/opendataservices-deploy/issues/102

OpenDataServices/opendataservices-deploy,OpenDataServices/opendataservices-deploy