add s3 support for repository

[tmanninger]

This PR adds support to manage s3 repository.

Example:

    elasticsearch::snapshot_repository {  's3_repository':
      repository_type => 's3',
      bucket          => $backup_aws_s3_bucket,
      region          => $backup_aws_s3_region
    }

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[cla-checker-service]

❌ Author of the following commits did not sign a Contributor Agreement:
a511986

Please, read and sign the above mentioned agreement if you want to contribute to this project

[vox-pupuli-tasks]

Dear @tmanninger, thanks for the PR!

This is Vox Pupuli Tasks, your friendly Vox Pupuli Github Bot. I noticed that your pull request has CI failures. Can you please have a look at the failing CI jobs?
If you need any help, you can reach out to us on our IRC channel voxpupuli on Freenode or our Slack channel voxpupuli at slack.puppet.com.
You can find my sourcecode at voxpupuli/vox-pupuli-tasks

[vox-pupuli-tasks]

Dear @tmanninger, thanks for the PR!

This is Vox Pupuli Tasks, your friendly Vox Pupuli GitHub Bot. I noticed that your pull request contains merge conflict. Can you please rebase?

You can find my sourcecode at voxpupuli/vox-pupuli-tasks