Adds TarResource and CopyTo functions to be used for creating archives for use with the new `docker cp` behavior. Adds multiple test cases for the CopyFrom and CopyTo functions in the pkg/archive package. Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn) Upstream-commit: a74799b701f5a70e964ec528c6d731c8c93019e6 Component: engine