Add support for es6 modules for boot scripts

lib/plugins/boot-script.js

@@ -66,6 +66,7 @@ function runScripts(app, list, callback) {
     debug('Requiring script %s', filepath);
     try {
       var exports = require(filepath);
+      if (exports.__esModule) exports = exports.default;
       if (typeof exports === 'function') {
         debug('Exported function detected %s', filepath);
         functions.push({

test/bootstrapper.test.js

@@ -81,6 +81,7 @@ describe('Bootstrapper', function() {
         'promiseFinished',
         'thenableStarted',
         'thenableFinished',
+        'umdLoaded',
       ]);
       done();
     });

test/executor.test.js

@@ -315,6 +315,7 @@ describe('executor', function() {
         'promiseFinished',
         'thenableStarted',
         'thenableFinished',
+        'umdLoaded',
       ]);
     });
   });
@@ -337,6 +338,7 @@ describe('executor', function() {
             'promiseFinished',
             'thenableStarted',
             'thenableFinished',
+            'umdLoaded',
           ]);
           done();
         });

test/fixtures/simple-app/boot/umd-script.js

@@ -0,0 +1,13 @@
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: loopback-boot
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+module.exports = {
+  default: function() {
+    process.bootFlags.push('umdLoaded');
+  },
+};
+Object.defineProperty(module.exports, '__esModule', {value: true});