move CreateKernelConfig to kernelcreation.py

src/pystencils/backend/kernelcreation/config.py

src/pystencils/backend/kernelcreation/context.py

src/pystencils/backend/kernelcreation/defaults.py

src/pystencils/backend/kernelcreation/iteration_space.py

src/pystencils/backend/kernelcreation/typification.py

src/pystencils/kernelcreation.py