Rename read/write to copyTo/From

[karllessard]

Renames NdArray.read(dstBuffer) to NdArray.copyTo(dstBuffer), and NdArray.write(srcBuffer) to NdArray.copyFrom(srcBuffer), to make more obvious the direction of the data flow of these methods.

This is somehow related to tensorflow/java#510, though I just modified the signature in NdArray and left the one in DataBuffer intact, since the read/write methods of these entities tries to replicate the behaviour of the get/put methods of the Java NIO buffers.

[Craigacp]

I think it's worth updating the javadoc with the version that had the old names in, otherwise it looks good.