docker rmi -f works with stopped containers + revamped error messages

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

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Update hack/dind to match the rest of our scripts

No functional changes here, just coding style and maintainability.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
check if the daemon is run as root on startup

This commit makes Docker throw an error if the daemon isn't started as
root.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
update AUTHORS

Docker-DCO-1.1-Signed-off-by: Bryan Matsuo <bryan.matsuo@gmail.com> (github: bmatsuo)
Add notes about git commit messages

This improves readability of commits a lot and is easy to
follow. I think most people follow those rules already. They are based
on http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html

Docker-DCO-1.1-Signed-off-by: Johannes 'fish' Ziemke <github@freigeist.org> (github: discordianfish)
FIXES #5398: pkg/graphdb build only dependent on cgo tag

Docker-DCO-1.1-Signed-off-by: Bryan Matsuo <bryan.matsuo@gmail.com> (github: bmatsuo)
Make Jerome Petazzoni a maintainer for dind

In the spirit of getting more contributors to maintain their
components.. I nominate @jpetazzo ot maintain dind (he's the original
author).

@jpetazzo I don't expect this to be too much load, but it's a good and
symbolic start :)

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

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Export syncpipe fields
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Split term files to make it easier to manage
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Export more functions from libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Remove command factory and NsInit interface from libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Integrate new structure into docker's native driver

This duplicates some of the Exec code but I think it it worth it because
the native driver is more straight forward and does not have the
complexity have handling the type issues for now.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix execin with environment and Enabled support
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Make native driver use Exec func with different CreateCommand
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Remove container.json from readme

No need to duplicate this information when we already have a
container.json file in the root of libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Improve code/comment/output markings & display consistency

This PR aims to increase the consistency across the docs for
code blocks and code/comment/output markings.

Rule followed here is "what's visible on the screen should be reflected"

Issue:

 - Docs had various code blocks showing: comments, commands & outputs.
 - All three of these items were inconsistently marked.

Some examples as to how this PR aims to introduce improvements:

1. Removed `> ` from in front of the "outputs". Eg,
`    > REPOSITORY                 TAG       ID              CREATED` replaced with:
`    REPOSITORY                 TAG       ID              CREATED`.

2. Introduced `$` for commands. Eg,
`    sudo chkconfig docker on` replaced with:
`    $ sudo chkconfig docker on`

3. Comments:
`    > # ` replaced with:
`    # `.

> Please note:
> Due to a vast amount of items reviewed and changed for this PR, there
> might be some individually incorrect replacements OR patterns of incorrect
> replacements. This PR needs to be reviewed and if there is anything missing,
> it should be improved or amended.

Closes:
https://github.com/dotcloud/docker/issues/5286

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
Merge pull request #5515 from crosbymichael/refactor-libcontainer2

Remove CommandFactory and NsInit interface
drop CAP_SYSLOG capability

Kernel capabilities for privileged syslog operations are currently splitted into
CAP_SYS_ADMIN and CAP_SYSLOG since the following commit:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ce6ada35bdf710d16582cc4869c26722547e6f11

This patch drops CAP_SYSLOG to prevent containers from messing with
host's syslog (e.g. `dmesg -c` clears up host's printk ring buffer).

Closes #5491

Docker-DCO-1.1-Signed-off-by: Eiichi Tsukata <devel@etsukata.com> (github: Etsukata)
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)