Also show name of next navigator on the screen overlay

[haraldreingruber]

Especially for mob programming events, it can be very useful to show who will be the next navigator. This way the person is able to prepare itself to be ready and the rotation is usually performed quicker as the next navigator isn't selected "by surprise".

As this feature might not be that important to experienced groups, or groups working together frequently I would suggest making it optionally configurable via the settings.