Add support for AWS KMS

[omerlh]

To support kubernetes cluster running on AWS. Look like there is support for it in the dotnet SDK.
Open questions:

• Is KMS the right choice here? Maybe HSM is a better choice?
• How do we handle authentication to KMS/HSM? Pod IAM?

[max-lobur]

I made a note regarding auth: #120 (comment)
tl;dr don't. Just let AWS SDK figure out.
And use https://github.com/uswitch/kiam, or extend k8s node roles.

[shaikatz]

Done!