Upgrade to TensorFlow 2

[frauzufall]

I'll just use this issue to save some notes regarding the upgrade:

The new maven dependency for all operating systems (tensorflow-core-platform-mkl-gpu for GPU support though that didn't immediately work for me):

<dependency>
    <groupId>org.tensorflow</groupId>
    <artifactId>tensorflow-core-platform-mkl</artifactId>
    <version>0.2.0</version>
</dependency>

Example of how to create Tensors from arrays with the new API:

float[] imgArray = new float[height * width* channel];
// .. assign img values to array
Shape shape = Shape.of(1, height, width, channel);
Tensor tensor = TFloat32.tensorOf(NdArrays.wrap(shape, DataBuffers.of(imgArray)));

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