file2menu: Read a directory and display the content as links

This class can be used to generate a menu of links from the files contained in a given directory.

It can traverse recursively a given directory under the site document root and retrieve the list of files contained in the directory and any sub-directories that match a list of accepted file name extensions.

The class generates HTML to display the list of files as a menu of links. The menu can also be saved to a given file.