4.0.0

• Add configurable weight decay via WeightDecayChain
  • L1/L2 Decay
  • Decay to Init/EMA
• Remove decay_to_init flag. Use weight_decay_cls=tg.WeightDecayChain(tg.optim.WeightDecayToInit()) instead.
• Remove default_to_adam flag. Use default_to_baseline.