[bennu-portal] Complete Rewrite: Allowing more flexibility and integration

  * MenuItems are now split in MenuContainers and MenuFunctionalities
  * Added the concept of PortalBackend, allowing the various presentation technologies
    to integrate seamessly with bennu-portal
  * Added server-side layout injection for Backends that so require
[bennu-portal] Portal.js now uses Twig.js

  * Updated default theme accordingly
  * Twig.js is automatically loaded
  * Also improved handling of client-side modules in Twig.js
[bennu-admin] Completely rewritten the bennu-admin application

  * It is now built using Angular.js instead of Bankai
  * Updated to work with the new version of bennu-portal
  * Greatly improved the System Info panel, showing more JVM information and allowing Thread Dumps
  * Added a simple DomainBrowser UI, that allows navigating through the instance graph of the application