Add the Negative log likelihood activation and Softmax Output

[DantrazTrev]

https://ljvmiranda921.github.io/notebook/2017/08/13/softmax-and-the-negative-log-likelihood/

[exoushia]

Where should I add the likelihood function?

[DantrazTrev]

I would suggest adding the NLL as a separate function in the network.py. A new issue will be there just to enhance the CLI for this code
.