Add authenticated TLS support for API

Docker-DCO-1.1-Signed-off-by: Johannes 'fish' Ziemke <github@freigeist.org> (github: discordianfish)
configurable dns search domains

Add a --dns-search parameter and a DnsSearch
configuration field for specifying dns search
domains.

Docker-DCO-1.1-Signed-off-by: Daniel Norberg <daniel.norberg@gmail.com> (github: danielnorberg)
Docker-DCO-1.1-Signed-off-by: Aditya <aditya@netroy.in> (github: netroy)

document `DisableNetwork` config flag
fix typo in documentation

Docker-DCO-1.1-Signed-off-by: Daniel Norberg <daniel.norberg@gmail.com> (github: danielnorberg)
variable declaration cleanup

Docker-DCO-1.1-Signed-off-by: Daniel Norberg <daniel.norberg@gmail.com> (github: danielnorberg)
Merge pull request #3774 from danielnorberg/dns-search-domains

configurable dns search domains
Merge pull request #4703 from netroy/patch-1

Document the missing `DisableNetwork` config flag to /containers/create end-point
Merge branch 'https_client' of github.com:discordianfish/docker into discordianfish-https_client

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge branch 'master' into discordianfish-https_client

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
add a link to the security documentation when we mention the docker group (or -G)

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
Merge pull request #4784 from SvenDowideit/reference-security-doc

add a link to the security documentation when we mention the docker group (or -G)
Make ENV accept multiple vars for a single layer

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)
Initial work cleaning up some of the multi-env code

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)