added S3 versioning support

[alexeip0]

• added ability to get/delete specific version of an object
• added ability to list all versions of the bucket objects

[bji]

Thank you for your great changes, as you can see i don't really have anything to do with this project any more and I have not been particularly good about merging pull requests in a timely fashion, but your work is appreciated. Please just address the minor issue I raised above and I will merge this request.

[alexeip0]

Sorry, having hard time finding the minor issue I have to address. Is there a comment somewhere I'm not seeing?

[bji]

The minor issue is the question I asked above ... you have documented the version id as being 'null' if the object was created before versioning was available ... I think that the comment should be updated because it's ambiguous: 'null' could mean the string "null" or it could mean the zero-value null ... just wanted the docs to be clearer there.