Add support for Amazon Glacier (AWS.Glacier)

Change summary:

* RestJson: Support extracting output keys from headers
* RestJson: Support input/output (+streaming) payloads
* Glacier: Added client with tree hash computation method (computeChecksums) available as a public method that can be used to calculate tree hash. This is needed for multi-part uploads.
* Guides: Added example guides for single and multi-part uploading of archives in doc-src/guide/Examples.md