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/webpack.config.js

@@ -0,0 +1,12 @@
+const config = require('flarum-webpack-config');
+const webpack = require('webpack');
+const merge = require('webpack-merge');
+
+module.exports = merge(config(), {
+  output: {
+    library: 'flarum.core'
+  },
+  plugins: [
+    new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/)
+  ]
+});