New: Cleanup UI tooling, Update to Webpack 4, Gulp 4 (#655)

* New: Webpack 4

* New: Gulp 4

* New: Transpile UI for old browsers

Co-Authored-By: Mark McDowall <markus101@users.noreply.github.com>

frontend/babel.config.js

@@ -0,0 +1,35 @@
+const loose = true;
+
+module.exports = {
+  plugins: [
+    // Stage 1
+    '@babel/plugin-proposal-export-default-from',
+    ['@babel/plugin-proposal-optional-chaining', { loose }],
+    ['@babel/plugin-proposal-nullish-coalescing-operator', { loose }],
+
+    // Stage 2
+    '@babel/plugin-proposal-export-namespace-from',
+
+    // Stage 3
+    ['@babel/plugin-proposal-class-properties', { loose }],
+    '@babel/plugin-syntax-dynamic-import'
+  ],
+  env: {
+    development: {
+      presets: [
+        ['@babel/preset-react', { development: true }]
+      ],
+      plugins: [
+        'babel-plugin-inline-classnames'
+      ]
+    },
+    production: {
+      presets: [
+        '@babel/preset-react'
+      ],
+      plugins: [
+        'babel-plugin-transform-react-remove-prop-types'
+      ]
+    }
+  }
+};