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

.babelrc

@@ -1,7 +1,25 @@
 {
-  "presets": ["es2015", "react"],
+  "presets": [
+    "es2015",
+    "react",
+    [
+      "env",
+      {
+        "loose": true,
+        "modules": false
+      }
+    ]
+  ],
   "plugins": [
+    "transform-react-jsx-source",
+    "transform-react-jsx-self",
     "transform-decorators-legacy",
-    "transform-object-rest-spread"
+    "transform-object-rest-spread",
+    [
+      "react-intl",
+      {
+        "messagesDir": "./build/messages"
+      }
+    ]
   ]
 }