Merge branch 'gpu-support' into 'develop'

README.md

declearn/model/api/_model.py

declearn/model/api/_vector.py

declearn/model/sklearn/_np_vec.py

declearn/model/sklearn/_sgd.py

declearn/model/tensorflow/__init__.py

declearn/model/tensorflow/_model.py

declearn/model/tensorflow/_vector.py

declearn/model/tensorflow/utils/__init__.py

declearn/model/tensorflow/utils/_gpu.py

declearn/model/tensorflow/utils/_loss.py

declearn/model/torch/__init__.py

declearn/model/torch/_model.py

declearn/model/torch/_vector.py

declearn/model/torch/utils/__init__.py

declearn/model/torch/utils/_gpu.py

declearn/test_utils/_vectors.py

declearn/utils/__init__.py

declearn/utils/_device_policy.py

test/model/model_testing.py