Adding bug fixes and acknowledgements to 2.9.1. Release Notes

Adding bug fixes and acknowledgements to 2.9.1. Release Notes

The structure of these point release notes is a little different from what
we did with the 2.8 series. I restructured the headings a bit so that there
is just the one level one header. The two headers in the 2.8 release notes
led to a confusing outline.

Also, I'm adding acknowledgements for each point release rather than adding the
entire batch at the bottom of the file. There are two reasons for this change:

1. The release notes in the official documentation are broken up into different
sections, whereas the ones on the downloads page are available all on one page.
In the official docs, it appeared as if everyone being acknowledged had
contributed to the .0 release, when, in actuality, some had contributed patches
in other point releases. By adding acknowledgements to every point release
section, it is clear who contributed to which release.

2. Consistent contributors get acknolwedgement for every point release they
contribute to, which is a nice thing to do.

Signed-off-by: Kathy Lussier <klussier@masslnc.org>