Move ZoL downloads to a dedicated host.

Github deprecated its download service and disabled the "Files" tab
and "Upload" button as announced here:

  https://github.com/blog/1302-goodbye-uploads

Copy the /download tree to a dedicated host and relink the web site.
Create README.md

Add a README file to satisfy the Github attribution warning about the
zfsonlinux.github.com repository.
Use https links to google groups

Access to google groups http urls recently started failing
with 404 errors.  Google wants us to use https.
Update FAQs for vdev_id

The udev helper zpool_id has been retired in favor of vdev_id which
incorporates all the previous functionality.  Update the web pages
to reference the new infrastructure.
Add FC18 and Ubuntu 12.10
Update main page for 0.6.0-rc14
Add /etc/zfs/zpool.cache generation section
Remove platforms pages

These pages are long since dead and should be removed.
Refresh for spl/zfs-0.6.1
Add supported platforms to fedora/epel pages
Reference refreshed zfs-release file for epel