Support IBM object storage

[andrenarchy]

For publishing history archives, it would be nice if the chart/images also supports the IBM cloud.

To do: Check whether this is already supported by the aws flavor of the Stellar Core image (via S3 API in IBM's object storage).

[todkap]

Can you share the library you use today for the aws flavor (or if it is just CURL). I can try to test it.

[andrenarchy]

Currently it's awscli, see https://github.com/satoshipay/docker-stellar-core/blob/8dac8b3df22f1e1ec92cde6f09caf3b54199b8c6/install.aws.sh#L8.