reorganized files and many changes

bob/learn/tensorflow/data/__init__.py

bob/learn/tensorflow/data/generator.py

bob/learn/tensorflow/data/tfrecords.py

bob/learn/tensorflow/dataset/__init__.py

bob/learn/tensorflow/dataset/image.py

bob/learn/tensorflow/image/filter.py

bob/learn/tensorflow/losses/BaseLoss.py

bob/learn/tensorflow/losses/ContrastiveLoss.py

bob/learn/tensorflow/losses/StyleLoss.py

bob/learn/tensorflow/losses/TripletLoss.py

bob/learn/tensorflow/losses/__init__.py

bob/learn/tensorflow/losses/center_loss.py

bob/learn/tensorflow/losses/mmd.py

bob/learn/tensorflow/losses/pairwise_confusion.py

bob/learn/tensorflow/losses/pixel_wise.py

bob/learn/tensorflow/losses/utils.py

bob/learn/tensorflow/losses/vat.py

bob/learn/tensorflow/metrics/__init__.py

bob/learn/tensorflow/metrics/embedding_accuracy.py

bob/learn/tensorflow/models/__init__.py