nngnorb should be a virtual server

* nngnorb.el: Declare it so in the call to `gnus-declare-backend'
Misspelled function name

* gnorb-registry.el (gnorb-delete-all-associations): Renamed from
  `gnorb-delete-all-assocations'.
New function for pruning dead associations

* gnorb-registry.el (gnorb-flush-dead-associations): New function.
  Removes gnorb-id values from registry entries when those values no
  longer point at existing Org headings.

Useful for when the registry is full of entries with the gnorb-id key
set, and pruning can't remove them.
Allow bulk association of messages

* gnorb-gnus.el (gnorb-gnus-incoming-do-todo): This function now
  respects Gnus' "work articles" concept, allowing users to mark
  multiple messages and bulk associate.
condition-case the incoming trigger process

* gnorb-gnus.el (gnorb-gnus-incoming-do-todo): If anything goes wrong
  with the incoming trigger process, we need to zero out
  gnorb-gnus-message-info and gnorb-gnus-capture-attachments.
Be more careful handling org tags on BBDB records

* gnorb-org.el (gnorb-org-popup-bbdb): Could be a string, could be a
  list. This is also an artifact of the new BBDB code that allows for
  lisp expressions as field values.
Update gnorb-registry-capture to use convenience funcs

* gnorb-registry.el (gnorb-registry-capture): Should be using
  `gnorb-bracket-message-id', and also `gnorb-registry-make-entry'. Was
  reduplicating effort