Example machine learning jupyterlab NBs

[newton1985]

Describe the user role
As an oSPARC user, I would like a bit of handholding in the development of machine learning projects. Specifically, building from existing examples would be useful.

Describe the goal
To build a neural network, even in the absence of significant prior experience. To this end, example notebooks showing how to interact with tensorflow and pytorch to build and train various networks would be helpful.

Describe the benefit
Building neural networks on oSPARC will be an important use case going forward, so it's good to offer as much support as possible.

Additional context
Refers to #332