= Admin Tree Structure

Originally created by Daniel Sheppard
Updated and put on github by Benny Degezelle and Keith Bingman because original server seems to be down.
Original announcement at http://lists.radiantcms.org/pipermail/radiant/2007-October/006597.html

Adds a structure to the page tree.

Pages can define a 'tree_children' method to return their children in
a more structured manner. The array returned from 'tree_children' 
should respond to enough methods to fool the _node.rhtml page to
render it like a page. It must respond to:

id
title
virtual?

and the class must respond to display_name.

If tree_children is defined and returns non-page objects, tree_child
should also be defined, returning the specific child for an alpha-numeric
slug.

*** THIS EXTENSION REQUIRES THE 'SHARDS' EXTENSION TO BE INSTALLED ***

This extension provides ArchivePage with two levels of drill-down
(year and month) and should be referenced as an example.