Add support for `RUN [""]` in Dockerfiles for greater specificity in what is actually executed

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3500 from tianon/lvm2-version

Add more specific lvm2 version to PACKAGERS document
Stop ADD from following symlinks outside the context when passed as the first argument

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3539 from jeandalido/patch-1

Update docker_remote_api_v1.8.rst
Merge pull request #3551 from tianon/test-docker-io-gpg-fingerprint

Inline the test.docker.io fingerprint in the install.sh script as well
Merge pull request #3554 from tianon/ubuntu-dep

Add ca-certificates to our package Recommends
add info and example of image cache in use when building

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)

Docker-DCO-1.0-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Don't shell out to tar for ExportChanges

This changes ExportChanges to use the go tar support so we can
directly create tar layer files. This has several advantages:

* We don't have to create the whiteout files on disk to get them
  added to the layer

* We can later guarantee specific features (such as xattrs) being
  supported by the tar implementation.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Discard all data on devicemapper devices when deleting them

This works around the fact that deleting a device in a thin pool
doesn't discard the free space. Unfortunately even this is not perfect,
as it seems discards are respected only for blocks that has never been
shared in the thin device code. However, this has been fixed in the
upstream kernel device-mapper tree:

http://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=0ab1c92ff748b745c1ed7cde31bb37ad2c5f901a

When this hits the kernel I belive this will fully return space
for removed images/containers to the host FS. For now it only
helps partially (which is better than nothing).

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Merge pull request #3544 from SvenDowideit/build-image-cache

add info and example of image cache in use when building
Use https to get the latest docker version

To avoid unexpected results since docker was using http.
For instance, my broadband doesn't return not found when it's down but
a html page saying that the internet is down. Docker was showing that
html instead of ignoring it.

Fix #3570

Docker-DCO-1.1-Signed-off-by: Fabio Falci <fabiofalci@gmail.com> (github: fabiofalci)
Add xz-utils to our deb-recommends since it's necessary for some images

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Port 'docker images' to the engine API

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Add compat 1.8

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
add legacy compat

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
move legacy stuff outside the job

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #3575 from shykes/engine-get-images

move `docker images` to a job
Fixes 3497
Docker-DCO-1.1-Signed-off-by: Andy Rothfusz <github@developersupport.net> (github: @metalivedev)
Fix docs Dockerfile to install correctly again

Previously we've been getting:

```
Step 6 : RUN pip install Sphinx==1.1.3
 ---> Running in 397eab32f57a
 Wheel installs require setuptools >= 0.8 for dist-info support.
 pip's wheel support requires setuptools >= 0.8 for dist-info support.
 Storing debug log for failure in /.pip/pip.log
 2014/01/13 18:01:34 The command [/bin/sh -c pip install Sphinx==1.1.3] returned a non-zero code: 1
 make: *** [docs] Error 1
```

This fixes that by telling pip not to use sudo to install (since we're already root).

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3584 from tianon/fix-docs-dockerfile

Fix docs Dockerfile to install correctly again