add Cmd::Subject::Help, vaporcalc fixes

	modified:   bin/vaporcalc
	new file:   lib/App/vaporcalc/Cmd/Subject/Help.pm
	modified:   lib/App/vaporcalc/CmdEngine.pm
Role::UI fixes

	modified:   lib/App/vaporcalc/Role/UI/Cmd.pm
	modified:   lib/App/vaporcalc/Role/UI/PrepareCmd.pm