docs(menu): add example of nested menus using dynamic data

#### Bug, feature request, or proposal:
Feature Request - Menu Docs

#### What is the expected behavior?
The docs would include an example of building a menu from a data structure similar to the [radio button docs](https://material.angular.io/components/radio/examples).

#### What is the current behavior?
The [menu docs](https://material.angular.io/components/menu/overview) only include a nested menu example using static HTML.

#### What are the steps to reproduce?
Working on a Stackblitz demo atm...

#### What is the use-case or motivation for changing an existing behavior?
This is a common use case for building application menus, especially for business applications. The data may come from a config file, a REST API, or some other source but it is very often not static and does not align with a static HTML example.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
Angular 4.4.3
TypeScript 2.3.4
Chrome 61
OS X El Capitan

#### Is there anything else we should know?
Thank you for your hard work on this library!

先查看菜单文档，并将其中静态的嵌套菜单示例与单选按钮文档中的动态数据模式进行比较。如果可以，请查看已报告的 StackBlitz 演示。完成的标准是：菜单文档包含一个基于数据结构构建的可正常工作的嵌套菜单示例，并且从示例中可以清楚地了解其行为。

由索引模型根据 Issue 内容生成。