Update the packpage using setup.py

[zhucaoxiang]

Hi, I revised the python files so the package now can be installed using setup.py. For example, pip install -e . or python setup.py install. In principle, it can be also uploaded to PyPI and distributed over the internet. But it probably needs some advanced techniques because of the Fortran libraries. This can be done in the future.

[spollok]

@zhucaoxiang Thank you very much for your pull request. I have tested it successfully on my Linux machine and have merged your changes now. Later, I will make some adjustments as some imports fail when not building the package.