Revamp freebsd.org/gnome index page

• Update to include mate and cinnamon.
• Fix some indention issues.
• Shuffle some text around, and remove some obsolete items.
• Only show the 5 most recent news items.
• Remove the gnomedesktop.org rss news channel parser. It doesn't work and is comment out to begin with.
• Update Resources links. Add our wiki, upstream gnome news, mate and cinnamon project sites. Remove obsolete links.

Approved by: rene@
Differential Revision: https://reviews.freebsd.org/D5130