Add support for sse-s3 encryption with vault as KMS.
Also refactoring code to make use of headers and functions defined in
crypto package and clean up duplicated code.
Internally, triton-go, what manta minio is built on, changed it's internal
error handling. This means we no longer need to unwrap specific error types
This doesn't change any manta minio functionality - it just changes how errors are
handled internally and adds a wrapper for a 404 error
Manta is an Object Storage by [Joyent](https://www.joyent.com/)
This PR adds initial support for Manta. It is intended as non-production
ready so that feedback can be obtained.
