Upgrade to webpack 4 and webpack-dev-server 3 (#1138)

Speeds up performance of webpack-dev-server.

web/app/package.json

@@ -30,8 +30,8 @@
     "sinon": "^4.1.2",
     "sinon-chai": "^2.14.0",
     "sinon-stub-promise": "^4.0.0",
-    "webpack": "^3.5.6",
+    "webpack": "^4.1.12",
-    "webpack-dev-server": "^2.7.1",
+    "webpack-dev-server": "^3.1.4",
     "whatwg-fetch": "^2.0.3"
   },
   "devDependencies": {
@@ -57,6 +57,7 @@
     "postcss-import": "^11.1.0",
     "postcss-loader": "^2.1.5",
     "style-loader": "^0.21.0",
-    "url-loader": "^1.0.1"
+    "url-loader": "^1.0.1",
+    "webpack-cli": "^3.0.7"
   }
 }

web/app/webpack.config.js

@@ -3,6 +3,7 @@
 const path = require('path');
 
 module.exports = {
+  mode: process.env.NODE_ENV === 'production' ? 'production' : 'development',
   entry: './js/index.js',
   output: {
     path: path.resolve(__dirname, 'dist'),
@@ -28,7 +29,7 @@ module.exports = {
             loader: 'eslint-loader',
             options: {
               fix: true,
-              emitWarning: process.env.NODE_ENV == 'development'
+              emitWarning: process.env.NODE_ENV === 'development'
             }
           }
         ]
@@ -46,7 +47,7 @@ module.exports = {
         use: [
           {
             loader: 'file-loader',
-            options: { publicPath: 'dist/' }
+            options: {}
           }
         ]
       }