The new outputs allow printing senders, recipients or both of matching
messages. To print both, the user can use --output=sender and
--output=recipients simultaneously.
Currently, the same address can appear multiple times in the output.
The next commit will change this. For this reason, tests are
introduced there.
We use mailbox_t rather than InternetAddressMailbox because we will
need to extend it in a following commit.
This code is based on a patch from Jani Nikula.
This is the output from sphinx-quickstart, massaged a bit, along with
our existing man pages converted to rst.
A skeleton notmuch-emacs manual is also included. It is not suitable
for end user use yet.
