Add links to CFEngine 3.5, Getting Started, and Tutorials pages 

Added new-user.html page links to the pages listed above.

Note to Deb and Volker: These merges did not get committed during the previous cherry-pick (git cherry-pick -x 2a6dc50) where the new-users.html page was added to 3.5). Instead of spending time trying to create a new CP, I just decided to make manual changes.