notmuch-report.json: Add sections for open, accepted, and rejected motions

notmuch-report.json: Add sections for open, accepted, and rejected motions

So folks can find open votes at a glance and see the results of past
votes.  New tags are:

* oci::motion for the initial proposal
* oci::motion-accepted for the initial proposal once it has passed.
  I'm also using this for a "this proposal was accepted" message if
  one was sent to the list.
* oci::motion-rejected for the initial proposal once it has been
  rejected.  I'm also using this for a "this proposal was rejected"
  message if one was sent to the list.