Restructured so that:

* 'Upgrading' is limited to work that has to be done to upgrade from
  a current deployment to the new version.

* 'Changes' is a comprehensive, user-level description of changes and
  new features.

Conflicts:
	doc/sphinx/whats-new/changes-trunk.rst
	doc/sphinx/whats-new/index.rst
	doc/sphinx/whats-new/upgrading-trunk.rst