Observer mode

Add the option to watch someone else play.

How to imagine this? Something like:

1. Observe other player: the view follows a selected player. Players with accounts can block others from observing them directly.
2. Observe the map: you can freely move the view around the map.
3. Watch arena/soccer: you can look at a list of current arena/soccer games, with the list of players playing in them, and observe one if you want.
4. In 1v1 arena, observers could have a player doll standing outside of the map, cheering for the warriors. That way the players know how many people are interested in their fight.

Pros:
- We can watch Egzekutor hack everyone into pieces in the arena.
- People can potentially learn by watching pros play.
- Builds community.

Cons:
- Less players on average, since some of them might just observe instead.
- Rezoner needs to sleep between implementing two ideas.
- Makes the main menu even more complicated.