Ordered discrete autoencoder model.

def autoencoder_ordered_discrete():
  """Ordered discrete autoencoder model."""
  hparams = autoencoder_residual_discrete()
  hparams.bottleneck_noise = 0.05  # Use 0.8 for ordered.
  hparams.gan_loss_factor = 0.05
  hparams.add_hparam("unordered", True)
  return hparams