TensorFlow code in Tesseract

[amitdo]

All the files under src/lstm that stars with tf.

It is useless. There is no way to train a model in TF that Tesseract can use for inference.

Can we finally remove the TF code from Tesseract?

[stweil]

It's only remaining use for me is that the code shows how to add another OCR engine, for example to use Kraken models with optional GPU support (on my wish list).

[amitdo]

IIRC, the code in Tesseract uses some internal TF 1.x functionality instead of a stable API.

[stweil]

I think I can look in old releases how an OCR engine was added, so we can indeed remove the TensorFlow code now.