Material-ui: [Menu] Support for menu without default selected first item

[willemx]

When a Menu has no selected items, it always has a highlighted first item.

• [x] I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

If I open a menu that has no item with select={true} I would expect the menu to open with the first item highlighted for as long as the cursor is hovering over it and then when the cursor moves to another item, the first item should be un-highlighted. So, only the item that is under the cursor should be highlighted if there is no selected item.

Current Behavior

When the menu (with no selected items) opens, the first item is highlighted and remains highlighted (suggesting that it is somehow selected) while the cursor hovers over other items.

Steps to Reproduce (for bugs)

See simple menu demo

Context

I am using a Menu to display a list of commands/actions that a user might want to execute. So I should like the menu to highlight only the command that the user is currently hovering over with the mouse. (Or on a touch device, no command should be highlighted)

Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 1.0.0. beta 17 |
| React | |
| browser | |
| etc | |

[oliviertassinari]

Duplicate of #5186

[AlexYegupov]

seems