Add favicon to docs.jboss.org

http://docs.jboss.org misses favicon
example: http://docs.jboss.com/gatein/portal/3.1.0-FINAL/user-guide/en-US/html/index.html

We need only to put under http://docs.jboss.org/favicon.ico our favicon like we have under http://www.jboss.org/favicon.ico