turn webpack middleware into middleware

fix HMR middleware, and some loopback boilerplate cleanup

server/middleware/webpack-hmr.js

@@ -0,0 +1,12 @@
+const webpackHotMiddleware = require('webpack-hot-middleware');
+const webpack = require('./helpers/webpack');
+
+const isProduction = (process.env.NODE_ENV === 'production');
+
+module.exports = (params) => {
+  if (isProduction || params.enabled !== true) return (req, res, next) => next();
+
+  const middleware = webpackHotMiddleware(webpack.compiler);
+
+  return (req, res, next) => middleware(req, res, next);
+};