kernel config in userguide

["Justin C. Sherrill" <justin@xxxxxxxxxxxxxxxxxx>]

http://forknibbler.com/guide/kernelbuild.html

A guide to configuring and updating the kernel.  It's a bit short, but I
want to have something before 1.0.  Comments?  Corrections?  I'm still a 
bit vague on when quickworld/quickkernel is preferred over 
buildworld/buildkernel.