Release notes: clean up and introduce TPAC

Release notes: clean up and introduce TPAC

General clean-up of the release notes for consistency and to support
PDF output:

* Reformat line-widths to 80 characters or less
* Mark interface window and element names as bold
* Fix up some formatting glitches and headers
* Make the "Documentation is available..." note standard & separated
  by one line; I suspect we will want to modify this globally, so it
  will be easier if it is consistent.

Also, give a brief introduction to the TPAC and mention the forthcoming
JSPAC deprecation in the next feature release.

Signed-off-by: Dan Scott <dan@coffeecode.net>