Adds Docker Image v1 Spec Documention

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)
yep: https://github.com/docker/docker/blob/master/docs/sources/contributing/docs_style-guide.md#style-standards I'll wrap all the lines which extend past 80 columns.