Adds support for sysctl options in docker services.
* Adds API plumbing for creating services with sysctl options set.
* Adds swagger.yaml documentation for new API field.
* Updates the API version history document.
* Changes executor package to make use of the Sysctls field on objects
* Includes integration test to verify that new behavior works.
Essentially, everything needed to support the equivalent of docker run's
`--sysctl` option except the CLI.
Includes a vendoring of swarmkit for proto changes to support the new
behavior.
Signed-off-by: Drew Erny <drew.erny@docker.com>