remove the JsonWrapper class

Let's follow the Google Style Guide, in which private variables are
simply suffixed with "_". It's a sign, not a cop, but that's fine.
I'd rather keep things simple, and code review should suffice for
catching uses of a private variable outside the class.

webpack/base.config.js

@@ -81,9 +81,6 @@ module.exports = (env, args) => {
       ],
     },
     plugins: [
-      new webpack.DefinePlugin({
-        'process.env.NODE_ENV': JSON.stringify(args.mode),
-      }),
       new webpack.IgnorePlugin(/\.\/locale$/),
       new HtmlWebpackPlugin({
         title: nvrSettings.app_title,