s3 ACL Grantee class is missing support for by-email and by-uri

[DreamHost]

See the docs here:
  http://docs.amazonwebservices.com/AmazonS3/2006-03-01/API/RESTObjectPUTacl.html

Only the first option for Grantee values is implemented in txAWS.

[Duncan McGreggor (oubiwann)]

I think that defining a Grantee by URI might be required in order to support canned ACLs, for instance, "public-read," since under the hood, the canned ACL for public read does this:

    <Grant>
      <Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Group">
        <URI>http://acs.amazonaws.com/groups/global/AllUsers</URI>
      </Grantee>
      <Permission>READ</Permission>
    </Grant>