Add Pytorch dependencies

This change adds Pytorch dependencies using CMake and a unified model class. Currently, I assume the model takes integer inputs and outputs integers as well. If the data type is wrong, please let me know.

Furture commit will include unit test for this class. I'm thinking of loading a dummy pytorch that multiplies each input with a constant. With this test, I can ensure that the class gets expected output and works without unexpected behaviors. (The dummy model is quite easy, I've done that already)