Keyboard Accessible MenuItems and VolumeMenuButton

Makes the volume control and menu items accessible via tab navigation on the keyboard.
Fix for #1517 
@gkatsev I'm realizing that the volume menu button is broken by default because `vertical` is true by default here and nothing else is set up to handle that. If I set it to false it makes it work. Does the BC version set this to true somewhere or would that change break things?