[R--gR] gR web page updated

It's great to see so much going within gR: I tried to reflect the latest
advances on the gR web page
  http://www.R-project.org/gR/
by adding prominent links to the release announcements.

I also tried to update the list of CRAN packages somehow related to gR.
In addition to the packages announced on this list, two interfaces to
BUGS became available as CRAN packages.

Let me know if I missed anything.

For the CRAN package authors (i.e. in particular Claus, Jens Henrik,
Mathias, S?ren): I guess it would be a good idea to announce the new
packages on the R-packages list
  https://stat.ethz.ch/mailman/listinfo/r-packages
(which is sort of under-used anyway). Probably, you'll gain a few more
interested users (i.e., potential bug-fixers etc.) by doing so.

Best wishes,
Achim