move git clone from daemon to client

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

add a little doc
if client has no git, use server

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Add initial logging to libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add stderr log ouput if in debug
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
update godoc and add MAINTAINERS for mflags

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Fix spelling of benchmark test

Docker-DCO-1.1-Signed-off-by: Paul Nasrat <pnasrat@gmail.com> (github: pnasrat)
Fix external link on security of containers

Docker-DCO-1.1-Signed-off-by: Vladimir Rutsky <altsysrq@gmail.com> (github: rutsky)
Merge pull request #4698 from rutsky/external_link_in_rst_fix

Fix external link on security of containers
Merge pull request #4672 from vieux/update_godoc_mflags

update godoc and add MAINTAINERS for mflags
fix content-type detection in docker cp

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #4686 from pnasrat/benchmark-typo

Fix spelling of benchmark test
Merge pull request #4700 from erikh/2371-sort_ports

In `docker ps`, sort by port instead of unsorted.
refactor(libcontainer): rename to CapabilitiesMask

The Capabilities field on libcontainer is actually used as a mask.
Rename the field so that this is more clear.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
chore(libcontainer): small grammar fix in types_test

Someone probably got really used to typing er on the end of contain :)

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Merge pull request #4719 from philips/Capabilities-to-CapabilitiesMask

refactor(libcontainer): rename to CapabilitiesMask
Merge pull request #4720 from vieux/fix_content-type_cp

fix content-type detection in docker cp
Merge pull request #4645 from crosbymichael/add-logger

Add logger to libcontainer
display command display in docker ps

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #4364 from vieux/move_clone

move git clone from daemon to client
Merge pull request #4701 from erikh/4099-non_existent_file_no_error

Fix `docker cp` trying to untar files that do not exist.