Currently, initremote works, but not the other operations. They should be
fairly easy to add from this base.
Also, https://github.com/aristidb/aws/issues/119 blocks internet archive
support.
Note that since http-conduit is used, this also adds https support to S3.
Although git-annex encrypts everything anyway, so that may not be extremely
useful. It is not enabled by default, because existing S3 special remotes
have port=80 in their config. Setting port=443 will enable it.
This commit was sponsored by Daniel Brockman.
In particular, munge key filenames to comply with the IA's filename limits,
disable encryption, support their nonstandard way of creating buckets, and
allow x-amz-* headers to be specified in initremote to set item metadata.
Still TODO: initremote does not handle multiword metadata headers right.
