Separate building and python install

[IvDmNe]

Hello! I slightly modified CMakeLists and few other things to be able to install this package in python environment and to avoid using of Open3D in case the examples are not necessary.

Main changes:

• Main CMakeLists.txt: arguments to enable compiling python wrapper and C++ examples;
• patchworkpp/CMakeLists.txt: changes SHARED to STATIC (only with static linking python binaries are installed correctly) and moved Eigen requirement from base CMakeLists.txt;
• python_wrapper/CMakeLists.txt: added INSTALL command
• python examples: get rid of try...except in import pypatchworkpp
• Added bash script for minimal Open3D installation to visualize C++ examples. I tried to include fetching in CMakeLists to automate it, but without success.
• pyproject.toml: config file for python installation.

Now the project can be installed like any other python package with pip: pip install .

Maybe, You'd want to upload it to PyPI. This would be very useful!.

[seungjae24]

Hi @IvDmNe, thank you for contributing several useful functionalities!

I will check uploading it on PyPI :) Thank you for suggestion.