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!

Comienza con la documentación del menú y compara su ejemplo estático de menú anidado con el patrón de datos dinámicos de la documentación de los botones de radio. Revisa la demo de StackBlitz reportada, si está disponible. Se considera completado cuando la documentación del menú incluye un ejemplo funcional de menú anidado creado a partir de una estructura de datos, cuyo comportamiento quede claro a partir del ejemplo.

Escrito por el modelo de indexación a partir del texto del issue.