Mention the AMI copy function in tutorial and release notes

[tomuben]

Background

The AMI is only available in the AWS region where the release process runs. We need to mention this fact in the tutorial and the release notes. Also we should link to the AWS docu which describes how to copy an AMI to another regions.#66

Acceptance Criteria

1. Mention in the tutorial and release notes the fact that the AMI is only available in eu-central-1
2. Link to https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/CopyingAMIs.html