This was already used for external libraries. This commit
changes the order to be consistently 'New/Changed/Removed',
and adopts the pattern for configuration changes as well.
For improved scannability, the bullet points now start with
the name of the configuration setting(s), followed by a sentence,
with an optional ticket in brackets after the sentence(s).
* A number of bullet points under "Configuration changes" were
in fact, not configuration changes. These have been moved to
"New features" or "Other changes" for now.
* Add mention of the relevant configuration variable to some
of the release notes: $wgTidyDriver, `watchlistdays`,
$wgGroupPermissions, $wgGroupPermissions.
Also fix ReleaseNotesTest to count characters, not bytes,
this was causing it to count – as two, and € as three.
Change-Id: Ie89dac6408f8a8dafbf59efe73a11f4d282c0c6b
