add shellspec golden harness for the legacy make engine

- spec/golden/cases.txt: 69 black-box cases (CLI wrapper mode and make
  include mode) run in a hermetic sandbox with a mocked docker
- spec/golden/expected/*.txt recorded from this engine (baseline)
- make test / test-golden / golden-record / lint dev targets

spec/golden/expected/misc-help.txt

@@ -0,0 +1,52 @@
+Usage:
+make [target]
+
+Targets:
+test Run unit + golden tests
+test-unit Run unit tests only
+test-golden Run golden tests only (MYOS_ENGINE=legacy|cli)
+test-integration Run tests needing a real docker daemon
+golden-record Re-record golden expectations from the legacy engine
+lint shellcheck all shell sources
+help This help
+attach Attach to docker SERVICE
+bootstrap Configure system
+build Build application docker images
+clean Clean application and docker stuffs
+config View application docker compose file
+connect Connect to docker SERVICE
+deploy Deploy application dockers
+down Remove application dockers
+exec Exec command in docker SERVICE
+install Install application
+logs Display application dockers logs
+rebuild Rebuild application dockers images
+reinstall Reinstall application
+release Create release VERSION
+restart Restart application
+run Run a command in a new docker
+scale Scale SERVICE application to NUM dockers
+shutdown Shutdown all dockers
+start Start application dockers
+stop Stop application dockers
+tests Test application
+up Create application dockers
+update Update application files
+upgrade Upgrade application
+ssh Connect to first remote host
+
+Context:
+ENV local
+ENV_PATH @WD@
+DOCKER_MACHINE x86_64
+DOCKER_SOCKET_LOCATION /var/run/docker.sock
+DOCKER_SYSTEM Linux
+DOMAIN example.test
+APP myos
+APPS c411 dsh myos wbr wbr.old
+BRANCH lightning
+VERSION legacy-1.0-beta
+RELEASE
+COMPOSE_FILE @MYOS@/stack/myos/networks.yml
+DOCKER_REPOSITORY tester/myos/local
+[exit 0]