Refs #7864 -- Updates to documentation for the oldforms/newforms switch.

 * Moved forms.txt to oldforms.txt
 * Moved newforms.txt to forms.txt
 * Updated links and most references to "newforms" (there are a few sections that need a more significant rewrite).


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8020 bcc190cf-cafb-0310-a4f2-bffc1f526a37