Replace sprockets/browserify with Webpack (#2617)

* Replace browserify with webpack

* Add react-intl-translations-manager

* Do not minify in development, add offline-plugin for ServiceWorker background cache updates

* Adjust tests and dependencies

* Fix production deployments

* Fix tests

* More optimizations

* Improve travis cache for npm stuff

* Re-run travis

* Add back support for custom.scss as before

* Remove offline-plugin and babili

* Fix issue with Immutable.List().unshift(...values) not working as expected

* Make travis load schema instead of running all migrations in sequence

* Fix missing React import in WarningContainer. Optimize rendering performance by using ImmutablePureComponent instead of
React.PureComponent. ImmutablePureComponent uses Immutable.is() to compare props. Replace dynamic callback bindings in
<UI />

* Add react definitions to places that use JSX

* Add Procfile.dev for running rails, webpack and streaming API at the same time

config/webpack/loaders/assets.js

@@ -0,0 +1,12 @@
+const { env, publicPath } = require('../configuration.js')
+
+module.exports = {
+  test: /\.(jpg|jpeg|png|gif|svg|eot|ttf|woff|woff2)$/i,
+  use: [{
+    loader: 'file-loader',
+    options: {
+      publicPath,
+      name: env.NODE_ENV === 'production' ? '[name]-[hash].[ext]' : '[name].[ext]'
+    }
+  }]
+}