Implement batching

When we run `examples/1_SimpleNet/simplenet.py`, the final thing that's executed is effectively
```
a = [0.0, 1.0, 2.0, 3.0, 4.0]
model(torch.Tensor(a))
```

This would also work with batching e.g., 
```
a = [0.0, 1.0, 2.0, 3.0, 4.0]
model(torch.Tensor([a, a]))
```

We should enable calling batching in this way on the FTorch side, too.