Removed outdated "adminindex" command -- the same behavior is now far easier...

Removed outdated "adminindex" command -- the same behavior is now far easier and better done in a template, or perhaps a custom `AdminSite.index` function. Refs #5500.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8548 bcc190cf-cafb-0310-a4f2-bffc1f526a37