docs: link to news file and other resources
    
    In the website reorg we accidentally lost all links to the nice
    reformatted news.html file. Add a link on the front page, and
    also extend the download page table so that it includes links
    to API docs and news files for each module (where available)
    
    Signed-off-by: Daniel P. Berrange <berrange@redhat.com>