Also unit testing the new operators.

* adding unit tests

* ignoring failing tests

* removing ignore from unit tests

Unit testing the operation too.

Exposing also the `IsFinite` one.
Unit testing both operations.

- Concat
- LGamma
- Tanh
- Slice

* removing unused namespaces

* implementing Tensor to scalar and scalar to tensor conversions

Unit testing the gradient too.

Also unit testing all the operator cases.

Also unit testing all the operator cases.

Change nest.flatten to generic.

2: Upgrade Microsoft.ML.TensorFlow.Redist to v1.14.

This reverts commit e0e2bd13ef.