MatMenu: full size menu

#### Bug, feature request, or proposal:
It would be nice to have a full-size menu option for mobile or maybe the ability to adjust the x and y locations and size (height/width) of the overlay.

The overlay is being set by the component and forces the size of the menu and the only way to change this is to extend the mdMenu to allow for specific heights and widths of the menu as well as specific positioning. Or in my case create a component from scratch to do this.

#### What is the use-case or motivation for changing an existing behavior?
My main concern with this request is that it's not in the material spec, however the angularjs version of the menu does have width options.

#### Is there anything else we should know?
If this isn't a good feature for the menu, what would be the best approach to creating a full-size mobile menu?

En el issue no se menciona ningún archivo ni prueba. Empieza por localizar la implementación del overlay de MatMenu y revisa cómo controla actualmente el tamaño y la posición del menú; compara las opciones de ancho del menú de AngularJS. Se considerará terminado cuando exista un enfoque definido y probado para menús móviles de tamaño completo o una altura, anchura y posición configurables del overlay.

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