add linked containers to hosts file

Docker-DCO-1.1-Signed-off-by: Bryan Murphy <bmurphy1976@gmail.com> (github: bmurphy1976)
Add /layers/(name)/get api end point for extracting a single layer as a tarball

Docker-DCO-1.1-Signed-off-by: Bryan Murphy <bmurphy1976@gmail.com> (github: bmurphy1976)
Merge branches 'bmurphy1976-api-layer-get' and 'bmurphy1976-etc-hosts'