Added support for multiple endpoints in X-Docker-Endpoints header
Docker-DCO-1.1-Signed-off-by: Joffrey F <joffrey@docker.com> (github: shin-)
Add memory usage and max usage stats.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
Adding a test for blkio stats.

Also adds a test utility we can use for other cgroup tests.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
[Documentation - API] Add missing 'signal' parameter for /containers/:id/kill endpoint

Docker-DCO-1.1-Signed-off-by: Leo Unbekandt <leo.unbekandt@appsdeck.eu> (github: Soulou)
Fix bug in engine.Sender

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
engine/spawn: run an engine in a subprocess, remote-controlled by Beam

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
engine.Len returns the number of keys in an env

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge pull request #4576 from Soulou/4549-doc-kill-signal-param

Add missing 'signal' parameter for kill endpoint
Merge pull request #5199 from shin-/registry_mirrors_support

Added support for multiple endpoints in X-Docker-Endpoints header
Merge pull request #5431 from shykes/engine-len

engine.Len returns the number of keys in an env
Merge pull request #5394 from vmarmol/add-croup-memory-stats

Add memory usage and max usage stats.
Merge pull request #5412 from vmarmol/add-blkio-test

Adding a test for blkio stats.
Merge pull request #5422 from shykes/engine-spawn

engine/spawn: run an engine in a subprocess, remote-controlled by Beam
Fixes #5152 : symlink in volume path

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)