This patch does two things:
1) Add "compose list", which lists compose UUIDs and other basic info,
2) Fix up "blueprints list", "modules list", "sources list", and
"compose types" so their output is just a plain list of identifiers
This is the same as the output at the top level, just trimmed down to
only the options for a single subcommand. It's trigged by providing
"help" or "--help" as a subcommand option.
