Release notes cleanup

General release notes clean-up including the following:

* Fixing typos and grammatical errors. Thank you to paxed and remingtron
  for alerting me to some typos.
* Fixing up the section headers so that they don't go beyond 5 levels
  deep. In some cases, this invovled reorganizing content. I didn't trim
  content as suggested by dbwells, but there may be room for some more
  trimming.
* Renaming some things to reflect the name that is used in the staff
  client to make the release notes more accessible to the average user.
* Reorganizing some content in a logical order.

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