Adds Docker Image v1 Spec Documention

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)
it should be the same logic and is explained in the last paragraph of this section:

> - Extract all contents of each archive.
> - Walk the directory tree once more, removing any files with the prefix
    `.wh.` and the corresponding *file or directory* named without this prefix.