In commit v3.0.0-rc1~9 (Help: Rename 3.0 release notes to 3.0.0,
2014-02-19) we anticipated the possibility of bugfix-only release notes.
However, in practice we have no release notes for bug fix releases
because we do not cover bug fixes in release notes at all, only new
features.  Instead we've been updating the feature-level release notes
document in bug fix releases, treating errors in the document as bugs.

It makes more sense to maintain release notes at the feature-release
level, so rename the documents accordingly.  Also update the document
titles and intro text to refer only to feature versions and not bugfix
versions.