Add code for Pardot implementation to docs

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
registry: adding vbatts to the MAINTAINERS

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Add "Should-Start" cgroupfs-mount and cgroup-lite to sysvinit-debian init script

It's fine to list both here because "Should-Start" is a loose binding (ie, if the listed service exists, it'll be started first, but otherwise, this one will start without it).

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
remove addString and replace Tail

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
fix event removal

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Fix stdin handling in engine.Sender and engine.Receiver

This introduces a superficial change to the Beam API:

* `beam.SendPipe` is renamed to the more accurate `beam.SendRPipe`
* `beam.SendWPipe` is introduced as a mirror to `SendRPipe`

There is no other change in the beam API.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: fix a timeout bug in Sender/Receiver

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: slightly more stress-testing of Receiver/Sender to reproduce the hang problem

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge pull request #5687 from shykes/pr_out_engine_fix_a_timeout_bug_in_sender_receiver
Engine: ensure all pipes are properly closed by Receiver and Sender

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

[michael@docker.com: fix stdin closing in engine.Job.Run]
[michael@docker.com: fix fd leak in engine.Receiver.Run]
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)

Docker-Tested-By: Solomon Hykes <solomon@docker.com>
Docker-Tested-by: Michael Crosby <michael@docker.com>
Merge pull request #5713 from shykes/pr_out_engine_ensure_all_pipes_are_properly_closed_by_receiver_and_sender
beam/data: Message.GetOne() returns the last value set at a key

This is a convenience for callers which are only interested in one value
per key. Similar to how HTTP headers allow multiple keys per value, but
are often used to store and retrieve only one value.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: Env.MultiMap, Env.InitMultiMap: import/export to other formats

* `Env.MultiMap` returns the contents of an Env as `map[string][]string`
* `Env.InitMultiMap` initializes the contents of an Env from a `map[string][]string`

This makes it easier to import and export an Env to other formats
(specifically `beam/data` messages)

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: Receiver and Sender preserve Job.Env

When sending a new job to a `engine.Sender`, the corresponding
`engine.Receiver` will receive that job with its environment preserved.
Previously the job name, arguments and streams were preserved but the
env was lost.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
fix(daemon): ensure the /var/lib/docker dir exists

The btrfs driver attempts to stat the /var/lib/docker directory to
ensure it exists. If it doesn't exist then it bails with an unhelpful
log line:

```
2014/05/10 00:51:30 no such file or directory
```

In 0.10 the directory was created but quickly digging through the logs I
can't tell what sort of re-ordering of code caused this regression.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Dockerfile: updated ubuntu release used for builds

This patch just revs the Ubuntu release used for builds from 13.10
to 14.04.

Docker-DCO-1.1-Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> (github: cyphar)
Merge pull request #5635 from vbatts/vbatts-registry_maintainers
Start separating the image subsystem

This is a first step towards moving all code related to local
manipulation of images into a cleanly separated subsystem,
accessible via a stable set of commands in the engine API.

`graph.TagStore` now implements `engine.Installer`. For now, it
is installed by `Server.InitServer`, along with all other Server
commands. However this will change in future patches.

`graph.TagStore.Install` registers the following commands:

* `image_set` creates a new image and stores it locally.
* `image_get` returns information about an image stored locally.
* `image_tag` assigns a new name and tag to an existing image.

These commands are a pre-requisite for moving 'push' and 'pull'
out of `Server`.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge pull request #5432 from shykes/image-subsystem-1
Merge pull request #5716 from shykes/pr_out_engine_receiver_and_sender_preserve_job_env