add ec2-automate-backup-awscli to support aws cli tools

I've modified the ec2-automate-backup.sh script to use the aws cli tools instead of the ec2-* tools. Since my changes removed the option of using the ec2-* tools, I made a copy of script and renamed it. I've tested the following method of backing up and purging:

    ec2-automate-backup-awscli.sh -r us-east-1 -s tag -t 'Name=tag:Backup,Values=True' -k 31 -p -n