chain commands, and let a project refine a catalogue stack

myos build up logs host/fabio runs the three in order and stops at the first
failure, the way make build up logs STACK=host/fabio did. Leading words that
name commands are commands; the first word that is not one starts the stacks.

A stack found in several directories of the stack path is now merged rather
than shadowed, least specific first, so a project drops
stack/postgres/postgres.local.yml next to the catalogue's postgres.yml and
refines it. Settings hooks follow the same order, so a project can redefine a
default the catalogue ships. Neither engine did this before: the project
directory simply hid the catalogue one.

An unknown command now says so and suggests the command to type, instead of
printing the whole usage.

spec/golden/cases.txt

@@ -81,3 +81,6 @@ shim-up-group                   | shim-project  | @make up STACK=host DRYRUN=tru
 shim-config                     | shim-project  | @make config STACK=host/consul DRYRUN=true
 shim-project-target             | shim-project  | @make host-certs
 shim-env                        | shim-project  | @make env ARGS=COMPOSE_PROJECT_NAME STACK=host
+chain-build-up-logs             | host-project  | build up logs host/fabio
+chain-up-group                  | host-project  | up ps host
+chain-print-two                 | host-project  | print-COMPOSE_PROJECT_NAME print-APP STACK=host/consul