* Renaming DOCKER_ORCHESTRATOR to DOCKER_STACK_ORCHESTRATOR * Renaming config file option "orchestrator" to "stackOrchestrator" * "--orchestrator" flag is no more global but local to stack command and subcommands * Cleaning all global orchestrator code * Replicating Hidden flags in help and Supported flags from root command to stack command Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>