adds support for different accounts

[jritsema]

example:

harbor-compose migrate my-app dev \
  --account-name my-aws-account \
  --account-id 123456789012 \
  --vpc vpc-123 \
  --private-subnets subnet-123,subnet-456 \
  --public-subnets subnet-789,subnet-012 \
  --profile my-profile