[PATCH 00/11] add recipients to search output

[Jameson Graef Rollins]

This series is an attempt to add thread recipients to the search
output.

My personal overall goal of this series is to support the handling of
drafts in the emacs ui.  For drafts we want to see recipients, instead
of authors, in the search output.  I can imagine other uses for this
series as well, though.

The first four patches generalize the author list handling in thread
objects to handle any address list.  These patches could be applied
regardless of if the rest of the series is accepted.

After that we modify the thread constructor such that it can hold
thread recipients as well.  Since there is overhead in retrieving
thread recipients from the message files (recipients are not stored in
the database) this is handled with a switch.

Further patches add the new switch to the search CLI that adds thread
recipients to the structured output formats.  I didn't modify the text
output format, since there is no way to extend it.  I can imagine
tweaking the text output such that the author field is instead
replaced by the recipients (as is done for the emacs UI at the end of
the series), but that's not done here.

In the emacs UI, I add a new toggle function that will toggle display
of thread authors or recipients in the 'authors' field of the search
output.  It's unfortunate that this ambiguity in that field name
remains, but I didn't know how to change that cleanly.  I'm working on
some tests for the new emacs functionality that I'll include in the
inevitable v2 of this series.

The last patch is mostly just a tickle to suggest adding the
recipients to the database.  It would make the --include-recipient
searches much faster of course, but it might be overhead in the
database that folks aren't interested in.

As always, feedback, review, and comments are much appreciated.

jamie.