Merge CE master into EE master (bis)

This merges CE master (up until commit 10aa99a3) into EE master.

@ayufan: I think I managed to resolve the conflicts in the Ability class properly, could you double check just to be sure? Also I had to resolve some conflicts in app/views/projects/edit.html.haml regarding mirroring/project builds, could you check if the view still has everything in the correct order?

/cc @yorickpeterse