Autoload cookies all around

* lisp/gnorb-bbdb.el
* lisp/gnorb-gnus.el
* lisp/gnorb-org.el

Autoload cookies for all likely functions
Use existing functions for mime handles

* lisp/gnorb-gnus.el (gnorb-gnus-collect-all-attachments): Don't use
  random list access functions, there are proper functions for accessing
  mime info. They work better, use them.