list_directory(d, @optional ignore_hidden = true)
      
    Return a list of files in the directory d.
Ignore_hidden controls whether hidden-files will be returned.
      Under UNIX and Mac OS X hidden-files are those that start with a period (such as
      '.', '..', and '.profile'). A setting of false will enumerate all the files.
      A setting of true will only enumerate the files that are not hidden.
      A setting of 'dot_and_dot_dot will enumerate all the files except for the '.' and
      '..' hidden files.
list_directory("./Projects/slogan")
// [ChangeLog, configure, emacs, example,
    install, LICENSE, Makefile, packages, platform,
    README.md, src, test, TODO]
list_directory("./Projects/slogan", false)
// [., .., .git, .gitignore, ChangeLog,
    configure, emacs, example, install, LICENSE, Makefile,
    packages, platform, README.md, src, test, TODO]
list_directory("./Projects/slogan", 'dot_and_dot_dot)
// [.git, .gitignore, ChangeLog,
    configure, emacs, example, install, LICENSE, Makefile,
    packages, platform, README.md, src, test, TODO]