Change the default value of skip_duplicated_positions_in_training

[nodchip]

Setting skip_duplicated_positions_in_training option to 0 may improve elo. We will change the default values of skip_duplicated_positions_in_training. Before we change them, we need the following experiments:

1. Generate training data.
2. Train a net with 1., and skip_duplicated_positions_in_training = 0.
3. Train a net with 1., and skip_duplicated_positions_in_training = 1.
4. Compare the elo between 2. and 3.

Any helps are welcome.