use $ENV{HOME}/.b-datum/backup.conf as alternative

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>
Net::Amazon::S3 is not necessary for all cases

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>
typo for --use-own-storage

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>