make the hooks usable by the whole catalogue

- hooks load the _stack files of every directory between the stack path root
  and the stack, outermost first: make included both $(dir)/*.mk and
  $(dir)/*/*.mk, so a stack in a subdirectory saw its parent's settings
- a group may be declared in <group>/<group>.env, where the stack lives
- MYOS_STACK_DIR lets a hook read a file it ships next to itself
- myos_filter no longer confuses a literal * in a make pattern with a wildcard,
  and the list helpers no longer let the shell expand a * into filenames
- MACHINE, SYSTEM, HOST and DOMAINNAME join the framework variables a hook sees
- the make shim gains $(call myos-var,NAME), so a .mk target can read a
  setting that now lives in a hook, and it picks up the .mk of every stack
  directory rather than only the project's

lib/context.sh

@@ -55,6 +55,11 @@ myos_context_defaults() {
   myos_default_DOCKER_NETWORK()            { myos_network_private "$USER" "$ENV"; }
   myos_default_DOCKER_IMAGE_TAG()          { printf 'latest'; }
   myos_default_GIT_USER()                  { printf '%s' "$USER"; }
+  myos_default_HOST()                      { myos_addprefix "${HOSTNAME:-}." "$(myos_var DOMAIN)"; }
+  myos_default_HOSTNAME()                  { printf '%s' "${HOSTNAME:-}"; }
+  myos_default_DOMAINNAME()                { myos_firstword "$(myos_var DOMAIN)"; }
+  myos_default_MACHINE()                   { uname -m 2>/dev/null; }
+  myos_default_SYSTEM()                    { uname -s 2>/dev/null; }
   myos_default_HOST_COMPOSE_PROJECT_NAME() { printf '%s' "${HOSTNAME:-}"; }
   myos_default_HOST_DOCKER_VOLUME()        { printf '%s' "${HOSTNAME:-}"; }
   myos_default_HOST_DOCKER_REPOSITORY()    { printf '%s' "${HOSTNAME:-}" | tr '_-' '//'; }