Initial design idea for IO of archives, absolutely a WIP.

I'll try to port over the AR archiver to see how much effort the
switch from a stream based API to a channel based one would take.


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/compress/branches/compress-2.0@1556196 13f79535-47bb-0310-9956-ffa450edef68