Started refactor

src/pystencils/old/cpu/__init__.py

src/pystencils/old/cpu/cpujit.py

src/pystencils/old/cpu/kernelcreation.py

src/pystencils/old/cpu/msvc_detection.py

src/pystencils/old/cpu/vectorization.py

src/pystencils/old/gpu/__init__.py

src/pystencils/old/gpu/gpu_array_handler.py

src/pystencils/old/gpu/gpujit.py

src/pystencils/old/gpu/indexing.py

src/pystencils/old/gpu/kernelcreation.py

src/pystencils/old/gpu/periodicity.py

src/pystencils/old/kernelcreation.py

src/pystencils/old/transformations.py

src/pystencils/old/typing/__init__.py

src/pystencils/old/typing/cast_functions.py

src/pystencils/old/typing/leaf_typing.py

src/pystencils/old/typing/transformations.py

src/pystencils/old/typing/utilities.py

src/pystencils/placeholder_function.py

src/pystencils/rng.py