Remove the index.js indirection

Make index.es6 the main entry point.

src/index.js

@@ -1,23 +0,0 @@
-/*
- * Copyright (C) 2017 Red Hat, Inc.
- *
- * Cockpit is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License as published by
- * the Free Software Foundation; either version 2.1 of the License, or
- * (at your option) any later version.
- *
- * Cockpit is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this package; If not, see <http://www.gnu.org/licenses/>.
- */
-
-var cockpit = require("cockpit");
-
-document.addEventListener("DOMContentLoaded", function() {
-    var app = require("./index.es6");
-    app.run();
-});