Added functionalities around grid code generation, like accepting custom defined functions, exporting it to a file and saving it to grid_options

added function to parse arguments via commandline, added parsing of version history and and the loading of the generated grid function

added extra test files. there are new api functions im starting to put all of them into a test function now. later this will become a real unit test function

Rewrote argument handling of population class, added export functions. Added python-c-bindings to return store and other small changes