[pbmserv] New renju options

[zemljak@atlas.cz]

Attentions renju players:

Yamaguchi openings rule is implemented on PBeM.
Syntax for "challenge" command:

renju challenge first_player second_player -yamaguchi


Yamaguchi rule

1. First player puts 3 stones (from 52 openings, like with RIF
   standard rules + new 26 large openings), and at the same time,
   suggests how many alternative 5th moves to be made.
2. Second player decides to swap or keep as white and plays the 4th
   move.
3. When black plays the 5th move, he/she needs to play as many
   alternative 5th moves as suggested by tentative black when opening
   the game.
4. White chooses one of the 5th moves, and plays the 6th move.
5. Continue as RIF standard rules (with forbidden moves rule for
   black).