Webpack (#1367)

* Replace gulp with webpack and npm scripts for JS compilation
* Set up Travis CI to commit compiled JS
* Restructure `js` directory; only one instance of npm, forum/admin are "submodules"
* Refactor JS initializers into Application subclasses
* Maintain partial compatibility API (importing from absolute paths) for extensions
* Remove minification responsibility from PHP asset compiler
* Restructure `less` directory

js/src/admin/utils/saveSettings.js

@@ -0,0 +1,14 @@
+export default function saveSettings(settings) {
+  const oldSettings = JSON.parse(JSON.stringify(app.data.settings));
+
+  Object.assign(app.data.settings, settings);
+
+  return app.request({
+    method: 'POST',
+    url: app.forum.attribute('apiUrl') + '/settings',
+    data: settings
+  }).catch(error => {
+    app.data.settings = oldSettings;
+    throw error;
+  });
+}