GF home page: link to GF clouds service (cloud.grammaticalframework.org)

Also some small cloud service documentation updates.

index.html

@@ -36,6 +36,7 @@ March 2012
 | <A HREF="doc/gf-quickstart.html">QuickStart</A>
 | <A HREF="http://groups.google.com/group/gf-dev">UserGroup</A>
 | <A HREF="gf-book">Book</A><font size=-1 color=red><i>New!</i></font>
+| <a href="http://cloud.grammaticalframework.org/"><img src="src/www/P/gf-cloud.png" alt="GF Cloud Service" title="GF Cloud Service"></a>
 ] 
 </div>
 <div class=extralinks>