Cleaned up homepage, regenerated manual, added release script

[Mark Wielaard <mark@klomp.org>]

Hi,

I have cleaned up the homepage a bit by removing all explicit version
references and adding pointers to this mailinglist, bugzilla, git and
the (older) downloads. See the bzip2-htdocs git repo:
https://sourceware.org/git/?p=bzip2-htdocs.git;a=summary
anything committed there will automatically update the homepage:
https://sourceware.org/bzip2/

I regenerated the manual and other artifacts with the latest version.
To make everything look right I had to update the bzip.css for the new
layout (commit ddd8ba) and adjusted bz-html.xsl to make sure we
generate UTF-8 and explicitly include a link to the bzip.css stylesheet
(commit ac9b38).

To make it easy for others to do this whenever we do a new release
there is now a release-update.sh script (commit 32db5b). That uploads
the downloads and updates the webpages. For anybody in the bzip2 group
on sourceware.

Cheers,

Mark