Be more careful about what MIME parts we attach

lisp/gnorb-gnus.el: (gnorb-gnus-collect-all-attachments) Inline
		    attachments are okay as well -- so long as there's a
		    filename we're probably okay to attach
Declare some function, possibly unneccesary

lisp/gnorb-gnus.el: Declare functions from org-gnus
Finer control over how attachments are saved

lisp/gnorb-gnus.el: (gnorb-gnus-collect-all-attachments) New extra
		    argument allows more control over when we save
		    attachment filenames into
		    `gnorb-gnus-capture-attachments' and when we don't.
		    We don't only save during capture, but also on
		    triggering incoming messages.
Possibly safer arguments to nnir group creation

lisp/gnorb-gnus.el: (gnorb-gnus-search-messages) This might be
		    superstitious, but it can't hurt to stick a
		    placeholder in for the group name
Largely re-wrote gnorb-gnus-outgoing-do-todo

lisp/gnorb-gnus.el: (gnorb-gnus-outgoing-do-todo) Clearer separation
		    between use cases: new messages that need to be
		    tracked, and replies to incoming messages that are
		    already tracked. More thorough checking of headers,
		    to ensure that we DTRT.
Clean up saved sent-message info

lisp/gnorb-gnus.el: (gnorb-gnus-outgoing-make-todo-1) Sets
		    gnorb-bnus-sending-message-info to nil when it's
		    done.
Unwrap "if" from around function

lisp/gnorb-gnus.el: (gnorb-gnus-incoming-do-todo) If we're raising an
		    error, there's no need to wrap the whole function in
		    the if clause
Clearer docstring

lisp/gnorb-bbdb.el: (gnorb-bbdb-open-link) Docstring a little clearer
Fix Agenda BBDB popup for searches with no tags

lisp/gnorb-org.el: (gnorb-org-popup-bbdb) Previously, if there were no
		   tags in the agenda search, *all* BBDB records with
		   org-tags fields were popped up. Oops.