lilypond authors, release notes, announcements

[Graham Percival]

It looks like we're getting close to the first release candidate.

- could any new contributors check:
  http://lilypond.org/authors.html
to make sure they're there?  if you have git access, you should
be in "development team", and choose your own title.  If not,
you should be listed in "current contributors", in whichever
categories you think is relevant.
Our list of translators looks particularly slim.
Send patches for:
  Documentation/included/authors.itexi

- who wants to write release notes?  Do it in the same style as
  previous ones.  Keep it brief because various places have
  size limits.

- based on the written policy:
http://lilypond.org/doc/v2.13/Documentation/contributor/major-release-checklist
  - we're not using any potential requirements.
  - I'm not paying any attention to "unsorted" stuff.  In
    particular, I'm not going to send any announcements anywhere
    other than lilypond.org.  If you think we should be sending
    announcements, then start making/updating a list.

Cheers,
- Graham