Allow tensors to be passed to the logger

[botcs]

WandB allows us to use histograms when we pass a tensor instead of a scalar.
In the current API I get the following error:

ValueError: `self.log(next_batch_pred, tensor([242, 143, 582, 190, 436, 260, 183], device='cuda:0'))` was called, but the tensor must have a single element. You can try doing `self.log(next_batch_pred, tensor([242, 143, 582, 190, 436, 260, 183], device='cuda:0').mean())`

It's understandable that for some loggers it might not be feasible, but it's sorta a missed opportunity.

Thanks!
Csabi