xo::parameter

	// command implementation view

	set?	bool	has user-specified information
	string		string	the user-specified information
	value		any	actual value, user-specified
				transformed, or default ...

	// general acessors

	name        
	description 
	ordered     
	cmdline     
	required    
	list        
	hasdefault  
	default     
	generator   
	interactive 
	prompt      
	validator
	when-complete

xo::config

	names		list of all parameter names in the
			collection.
	@NAME		forward to parameter NAME, value()
	@NAME ...	forward to parameter NAME, specific
	      		method and args.

xo::private, xo::officer

	do ...		parse command line ...
	help		return help structure for command.

	//superclass methods (actor)

	name
	fullname
	name:
	description
	description:
	super
	super:
	keys
	get
	set

xo::private
	// internal xo::config methods.

	names
	@NAME
	@NAME ...

Command prefixes in parameters:

	validator
		<V> validate X
		<V> default

	generator
		<G>

	when-complete
		<W> X
