Add BNN

[nmaarnio]

[msmiyels]

Hi @nmaarnio ,

finally, got the binary classification running as a bayesian approach. I'll start to integrate today and hope to make the PR by the end of next week 🚀.

There will be some restrictions like saving/loading (not possible yet), but the core method works fine so far.

Q:
We would need to stick to specific TensorFlow & TensorFlow Probability versions in the setup. Is there any issue with that ❓