Warning was:

```
  /localhome/seitz_local/projects/pystencils/pystencils/cache.py:15: DeprecationWarning: The 'cachedir' parameter has been deprecated in
version 0.12 and will be removed in version 0.14.
  You provided "cachedir='/localhome/seitz_local/.cache/pystencils'", use "location='/localhome/seitz_local/.cache/pystencils'" instead.
    disk_cache = Memory(cachedir=cache_dir, verbose=False).cache
```

This restructuring allows for easier separation of modules into
separate repositories later. Also, now pip install with repo url can be
used.

The setup.py files have also been updated to correctly reference each
other. Module versions are not extracted from git state

- test run again
- notebooks not yet

- sphinx detection is not reliable, e.g. jupyter notebooks have sphinx
  imported at startup -> no caching from notebooks
- explicitly added cached functions via autofunction to docs
- some functions do not support memory cache, because memory cache can't
  handle non-hashable parameters -> introduced diskcacheNoFallback
  decorator for these functions