[plumage.nqp] Add info command; make fixup_commands() data-driven; misc cleanups and improvements
[plumage.nqp] Add info command; make fixup_commands() data-driven; misc cleanups and improvements

* Add info command for displaying project metadata
* Add info command to usage output
* Make fixup_commands() data-driven instead of hard-coded
* Include more metadata about commands in %COMMANDS
* Prepare for more advanced command line parsing
* Canonify 'return ($foo)' to 'return $foo'
* Untabify

parrot/plumage,parrot/plumage