The sass sources now live in a project in GNOME, so they can be used in multiple projects like gnome-shell-extensions. Because of that, add gnome-shell-sass as a submodule and import the sass sources from it.
We don't have any bashisms in this file, so we may as well use sh. https://bugzilla.gnome.org/show_bug.cgi?id=722342
Creating the standard Autotools infrastructure and adding the first extensions (the Hello, World! provided by the wizard).