Add first draft code to generate CUDA kernels

src/pairs/analysis/__init__.py

src/pairs/analysis/devices.py

src/pairs/code_gen/cgen.py

src/pairs/coupling/parse_cpp.py

src/pairs/ir/kernel.py

src/pairs/mapping/funcs.py

src/pairs/sim/simulation.py

src/pairs/transformations/__init__.py

src/pairs/transformations/devices.py