add missing license headers in training scripts

training/data_loader/data_loader.py

training/example/create_unified_dataset.py

training/example/display_patches_dataset.py

training/example/sample_test.sh

training/tools/concatenate_dataset.py

.../Nn_Filtering_Set_0/1_generate_raw_data/bvi_dvc_to_yuv.py

...ts/Nn_Filtering_Set_0/1_generate_raw_data/div2k_to_yuv.py

...ipts/Nn_Filtering_Set_0/1_generate_raw_data/tvd_to_yuv.py

...et_0/2_generate_compression_data/generate_dataset_json.sh

...0/3_training_tasks/model_conversion/conversion_to_sadl.sh

...t_0/3_training_tasks/model_conversion/model_conversion.py

...raining_tasks/model_conversion/nn_model_for_conversion.py

...iltering_Set_0/3_training_tasks/training_scripts/Utils.py

...ering_Set_0/3_training_tasks/training_scripts/nn_model.py

...Set_0/3_training_tasks/training_scripts/start_training.sh

...ring_Set_0/3_training_tasks/training_scripts/train_YUV.py

...ing_Set_0/3_training_tasks/training_scripts/yuv10bdata.py

...ipts/Nn_Filtering_Set_1/Conversion/ChromaInter/convert.py

..._scripts/Nn_Filtering_Set_1/Conversion/ChromaInter/net.py

...ipts/Nn_Filtering_Set_1/Conversion/ChromaIntra/convert.py