Update wordpress.org/extend URLs

git-svn-id: https://plugins.svn.wordpress.org/wp-super-cache/trunk@960746 b8457f37-d9ea-0310-8a92-e5e31aec5664
Remove CDN Sync Tools. No longer in WP.org repo

git-svn-id: https://plugins.svn.wordpress.org/wp-super-cache/trunk@960747 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add Jetpack to mobile FAQ.

git-svn-id: https://plugins.svn.wordpress.org/wp-super-cache/trunk@960748 b8457f37-d9ea-0310-8a92-e5e31aec5664