Since version 4.5, Unity has a module manager menu option, but it seemed it was not yet implemented. In 4.6 however, that module manager is used for the new GUI system. The source of the new UI is also available now and the install instructions talk about a specific folder in the unity install to copy the files to. I experimented a bit with that folder to see if Unity is also able to load my own files/modules. The answer to that is YES.