Added new menu "Contribute" and "Resources"

Adjusted menu items accordingly

Added menu item to the new translations platform on https://www.transifex.com/projects/p/cakephp/

I'm not 100 % sure about the order of some items but I'm happy to hear suggestions.
Need to get rid of this. Can add links to the 2.6, 3.0 roadmaps on GH wiki.