This adds support for placement preferences in Swarm services. - Convert PlacementPreferences between GRPC API and HTTP API - Add --placement-pref, --placement-pref-add and --placement-pref-rm to CLI - Add support for placement preferences in service inspect --pretty - Add integration test Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com> Upstream-commit: 17288c611a4f3f75ecb3bbb4533820b1836c55a6 Component: engine