This diff allows users to set a max world population. That means that the population will be distributed evenly over all living players.
(Bunuses will be applied after this.)
An example: 300 max world pop cap. 3 players; Player 1 has +10% max pop cap. meaning that Player 1 has a max pop cap. of 110 and the other two players have a max pop cap. of 100.
Then Player 1 annihilates Player 2 compleatly. The 300 is redistributed over all living players: Player 1 max pop cap. is 165 (150 + 10%) and Player 3 has a max pop cap. of 150.
(Refs. #4504)