introduce basic array handling

src/pystencils/backend/ast/expressions.py

src/pystencils/backend/emission.py

src/pystencils/backend/kernelcreation/freeze.py

src/pystencils/backend/kernelcreation/typification.py

src/pystencils/backend/platforms/generic_cpu.py

src/pystencils/types/__init__.py

src/pystencils/types/basic_types.py

src/pystencils/types/quick.py