Add README.md file for the docker directory

See issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Docs: add ApiVersion to /version for remote API 1.12

Docker-DCO-1.1-Signed-off-by: Paul Morie <pmorie@gmail.com> (github: pmorie)
utils: add test for TimeoutConn

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Add integration test for history command and fix bug where history
would occasionally be returned in the incorrect order if sequential
layers had the same created time.

Docker-DCO-1.1-Signed-off-by: Bryan Murphy <bmurphy1976@gmail.com> (github: bmurphy1976)
Don't exit on eof in header reading in stdcopy

There was random lines drops in docker logs because of this
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
MAINTAINERS: add proppy for google.md

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Linking containers added to API example

Linking containers was not covered in the API documentation. I looked it up in the client source code and testing it manually.
Increase time before exit in TestMultipleAttachRestart

Sometimes third attacher attaching to already stopped container.
Also I've changed prefix to attach and fixed cleanup on Fatal.
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Add helper function to make prctl system call.
Docker-DCO-1.1-Signed-off-by: Mrunal Patel <mrunalp@gmail.com> (github: mrunalp)
Fix minor bug in contrib/man/md/md2man-all.sh causing the creation of contrib/man/manREADME

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Fix several man page spelling errors

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Fix missing leading slash for /bin/bash executable
Merge pull request #6429 from mika/patch-1

Fix missing leading slash for /bin/bash executable
Do inspect under container lock

It fixes some race conditions
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Fix several typos

Docker-DCO-1.1-Signed-off-by: Michael Prokop <github@michael-prokop.at> (github: mika)
Merge pull request #6431 from mika/mika/typos

Fix several typos
Fix spelling and grammar errors; remove seemingly out-of-place words

Docker-DCO-1.1-Signed-off-by: AJ Bowen <aj@gandi.net> (github: soulshake)
Fixed headers and ' characters

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Fixed DOCKER_OPTS

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
docker-java has moved to new location