Build Torch Extensions

Torch allows the user to define its own Torch Extensions with this mechanism : Custom C++ and CUDA Extensions. It does not work very well without CUDA so a different build path is taken in cmake definition.

cmake

Everything is defined in torch_extensions.cmake. It is a work going on.

setup.py

setup.py defines a custom command to call cmake. A line was added to copy the binaries into the main folder.