Basic structure for intrinsic-based vectorization

src/pystencils/backend/arrays.py

src/pystencils/backend/ast/__init__.py

src/pystencils/backend/ast/kernelfunction.py

src/pystencils/backend/ast/nodes.py

src/pystencils/backend/emission.py

src/pystencils/backend/jit/cpu_extension_module.py

src/pystencils/backend/platforms/__init__.py

src/pystencils/backend/platforms/generic_cpu.py

src/pystencils/backend/platforms/platform.py

src/pystencils/backend/transformations/__init__.py

...encils/backend/transformations/erase_anonymous_structs.py

src/pystencils/backend/transformations/vector_intrinsics.py

src/pystencils/backend/types/__init__.py

src/pystencils/backend/types/basic_types.py

src/pystencils/kernelcreation.py

tests/nbackend/kernelcreation/platform/test_basic_cpu.py