[development] New docs for multipage forms in drupal.org handbook

[Jeff Eaton]

A few months ago during the crazy dash to rewrite FormAPI, I wrote up a 
guide to making multistep forms and posted it to my blog. It's now been 
moved to the Drupal.org handbook at http://drupal.org/node/101707 where 
it can do more good.

It's a bit wordy, and it includes some historical background for 4.7 
that's probably unnecessary now, but to the best of my knowledge it's 
the only place that the nature of the #multistep flag is documented. :-) 
In the future I'd like to update the multistep example module in contrib 
to match this article, too.

--Jeff Eaton