Detect device (cpu or cuda) and use cuda if possible

CMakeLists.txt

decoder/src/Decoder.cpp

decoder/src/macaon_decode.cpp

reading_machine/src/Classifier.cpp

torch_modules/include/NeuralNetwork.hpp

torch_modules/src/NeuralNetwork.cpp

trainer/src/Trainer.cpp

trainer/src/macaon_train.cpp