merge existing config when committing

Fixes #1141

Docker-DCO-1.1-Signed-off-by: Wes Morgan <cap10morgan@gmail.com> (github: cap10morgan)
Show some ENV / local updated baseimage tricks that use an apt-cacher-ng proxy to make debian based installations instant

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
implement pharvey's suggestions

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
All caps variables in normal bash should be avoided not to accidentally collide with environment variables.

Docker-DCO-1.1-Signed-off-by: Rovanion Luckey <rovanion.luckey@gmail.com> (github: Rovanion)
Fix attach exit on darwin

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
improve deprecation message

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Update daemon docs and help messages for --iptables and --ip-forward

Fix docs and help messages of --iptables and --ip-forward to describe the true case behaviour

Docker-DCO-1.1-Signed-off-by: Ken ICHIKAWA <ichikawa.ken@jp.fujitsu.com> (github: ichik1)
Clean up the "go test" output from "make test" to be much more readable/scannable

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Exclude more "definitely not unit tested Go source code" directories from hack/make/test

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
fixes suggested by James

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
Merge pull request #4143 from SvenDowideit/apt-cacher-example

Show some ENV / local updated baseimage tricks that use an apt-cacher-ng...
Merge pull request #4526 from Rovanion/master

All caps variables in normal bash should be avoided not to accidentally collide with environment variables.
Update port_redirection.rst

Fix flags
Merge pull request #4603 from creack/fix_osx_attach

Fix OSX attach exit issue
Merge pull request #4604 from vieux/improve_deprecation_warning_flags

improve deprecation message
don't leave empty cidFile behind

This makes `--cidfile` clean up empty container ID files. These are
left behind when creating the container fails.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #4621 from unclejack/fix_empty_cidfile

don't leave empty CIDFile behind
Merge pull request #4492 from ichik1/add-ip-forward-to-docs

Update daemon docs for --ip-forward
Merge pull request #4619 from dgageot/patch-1

Update port_redirection.rst
Merge pull request #4000 from cap10morgan/1141-merge-configs-on-commit

merge existing config when committing