Fix memory problems with webpack-dev-server in dev mode (#2433)

Before this webpack was using hashes in filenames for the generated
files which are stored in memory. That meant on every change new files
have been generated and stored in memory, quickly filling up the
available memory.

With this change we do not use hashes for filenames in development mode
to avoid filling up memory.

Refs webpack/webpack#1914

graylog2-web-interface/webpack.config.js

@@ -85,6 +85,13 @@ if (TARGET === 'start') {
       inline: true,
       progress: true,
     },
+    output: {
+      path: BUILD_PATH,
+      filename: '[name].js',
+      publicPath: '/',
+      hotUpdateChunkFilename: "[id].hot-update.js",
+      hotUpdateMainFilename: "hot-update.json",
+    },
     plugins: [
       new webpack.HotModuleReplacementPlugin(),
       new webpack.DefinePlugin({DEVELOPMENT: true}),