Fix python bindings

[chjacob-tubs]

This is my attempt at getting the SWIG Python bindings back to work. It does the job for me, but I am sure the setup is not perfect (maybe a cmake expert can have a look, see "possible improvements" below). (Mostly fixes #63)

Changes:

• Adjusted paths to include files etc.
• Removed unnecassary / auto-generated files
• Use static linking for Python module

Possible improvements:

• I am sure the cmake setup can be improved. Apparently, there is a UseSWIG module now that could simplify things (but I didnt get it to work)
• Linking of the Python module to the dynamic library is not working, as the paths are not set correctly. This seems to be related to getting the RPATH set correctly, which seems to be difficult especially on MacOS. (I dont want to set another (DY)LD_LIBRARY_PATH only to get the Python module to work)
• The "make install" step is required to get a working python module (in the prefix/python directory). In the build directory, the file "xcfun.py" is missing. Dont know how to tell cmake to copy it there (or what the correct way of handling this is)

[codecov-io]

Codecov Report

Merging #67 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #67   +/-   ##
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  Coverage   42.29%   42.29%           
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  Files          78       78           
  Lines        1785     1785           
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  Hits          755      755           
  Misses       1030     1030

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[robertodr]

I am not familiar enough with SWIG to give comments off the top of my head. I'll check out this branch locally, test it out and give a more informed review.

[bast]

I think short-term this is fine. Long-term either pybind11 or CFFI since they provide a thinner interface.

[chjacob-tubs]

Thanks for the comments. Let me have another look before merging this, I will try to fix at least the copying/installation part ...

[robertodr]

Apologies that it took quite a bit to review this one. Being in another timezone did not compose well with being unfamiliar with SWIG. Still, great learning opportunity for me!

[chjacob-tubs]

I put some more work into this and now used UseSWIG instead of the manual setup that was used before. Please have a look, I think this is much nicer now. However, I didnt the RPATH stuff to work so I am still linking to the static library. To me, this is not a problem, but maybe you want to fix that.

I tested on MacOS and Linux with gcc. I am not sure whether switching to a different compiler will cause problems when building the Python shared library, because the Python libraries are usually built with gcc.

I also fixed the copying part, so the xcfun Python module can be used directly from the build directory.

[chjacob-tubs]

Sorry for removing FinfPythonLibsNew - I thought that was something obscure that I added at some point. I stand corrected. The target_include_directories is indeed required, but I made the linking part a bit nicer

[robertodr]

@bast I think once this is in we can:

1. Branch off release/v.2.0
2. Officially tag v2.0.0

[chjacob-tubs]

@robertodr @bast Let me fix the Python tests (#43) before doing the v2.0 release.

[robertodr]

Oh yes, of course! Thanks for reining in my enthusiasm :) Merging this one and closing #67