Implement upload to S3 hook

[hmeltaus]

Implement a new hook that uploads a file to an S3 bucket.

Configuration could look like this:

bucket: <target bucket>
key: <object key>
content: <content to upload, type>
iamRole: <optional iam role to use to upload>

When content is object or array, it will be serialized to json. Otherwise content will be used as is.