Support {2,3,5} players

[nymanjens]

Proposal for 2 players

• Double amount of tokens
• Double amount of starting units and coins, located in 2 different areas (e.g. France and Russia)

Differences with 1 playing for 2: Free coin trading

(See also this old bug: https://github.com/nymanjens/Alliances/issues/48)

Proposal for {3, 5} players

Same as above for one player.

Differences with 1 playing for 2: Free coin trading, can only resolve one move token per round