Allow placing black stones at the beginning of the game until a white one is placed. These stones are considered to be handicap stones. (not handicap if it was only one black stone).
Renamed updateValid etc. functions to onUpdateValid.
refs #61. The virtual board now gets updated every time a handicap stone is placed. The previous implementation waited until the first white stone was placed.
refs #61. Allow to still place handicap stones when the game initializing setup only contains black stones.
refs #61. Fixed bug when more then two handicap stones were placed successively.
Merge pull request #75 from augmented-go/#61_handicap

Closes #61 handicap