Release v0.60.4 tf.net and tf.keras v0.6.4.

released tf.net v0.60, keras v0.6.

uid_function for func_name

Add C API for TF_StringInit.

Release TensorFlow.NET v0.32, TensorFlow.Keras v0.3.

fix is_build_function in Layer.

release 0.20.

Supported for forced singlethreading

- Separated multithreading related methods to classname.threading.cs partial file
- ops: Added enforce_singlethreading(), enforce_multithreading()

v0.12 released

change text.