extended cmake support via command-line interface

src/pystencilssfg/cli.py

src/pystencilssfg/cmake/FindPystencilsSfg.cmake

src/pystencilssfg/cmake/__init__.py

src/pystencilssfg/cmake/modules/PystencilsSfg.cmake

tests/cmake_integration/.gitignore

tests/cmake_integration/CMakeLists.txt