And he scores!

- Player can now see the other player's level and score.
- Fixed a bug that made it seem like the other player's tetrominos were
falling at the same speed as the player's.
- newGame() does not longer change the state to Running (because that
made it look like the game started if the other player disconnected and
was generally not doing anything good).
- Disabled pause and restart functionality for now.
- Changed the 'You won' and 'Game over' texts and centered them.