Initial model for v2

[alejandromarcu]

This allows to start the training from a model stored in either wandb or a local file.
E.g.:

training:
  initial_model:
    wandb_project: B5W3
    wandb_alias: v160

[adamantivm]

One question: does this also pull the model from wandb and store it as onnx so that self-play can work with rust?

[alejandromarcu]

One question: does this also pull the model from wandb and store it as onnx so that self-play can work with rust?

Yes. The model is stored in wandb just as a pt, but when you specify the initial model, we create the AlphaZero agent with that model, and then we save it as model_0.pt and model_0.onnx if save_onnx=True.