added prelude and definitions

integration/MakeDemo/kernels.py

src/pystencilssfg/composer.py

src/pystencilssfg/context.py

src/pystencilssfg/emitters/cpu/basic_cpu.py

src/pystencilssfg/emitters/cpu/templates/BasicCpu.tmpl.cpp

src/pystencilssfg/emitters/cpu/templates/BasicCpu.tmpl.h