design.otl

Command
	organizable in a tree
	reusable in a process by command interpreter
	self-documenting
Debugging
	base Command class has fake debug() method
Twisted commands
	doLater() which returns a deferred
	who runs the reactor ?
		reactor should not be run() by default by command, since a command should be reusable in a process
		main function/program ?
		a specific ReactorCommand that is the root, or implements a command interpreter
Main program
	should instantiate the root command
	should invoke c.parse(args)