Build and perform the tests for all Python versions (Major change)

The unit and functional tests, as well as the example tests, can be built for all Python versions; i.e., the main version and the Python versions set via BORNAGAIN_PYTHON_PACKAGE_VERSIONS variable.

The tests for the extra Python versions are built by setting the variable BORNAGAIN_PYTHON_PACKAGE_TESTS=ON.

• A tests subfolder is added to the main binary directory to to store the built tests for the main version and their output.

• A tests subfolder is added to the build directory for Python packages to store the built tests and their output.

• Adapted unit and functional tests for multiple Python versions.
  NOTE:

  • Functional/PyEmbedded test still cannot be performed for the Python packages, most probably due to a problem with proper usage of the Python C/API. Currently, it is produced only for the main version.
  • The GUI test is performed only for the main version, since the Python packages does not include a GUI.

• A new CMake module MakePythonAPI is introduced to produce the Python interfaces to the C++ libraries. MakePythonAPI includes the necessary CMake code to build the Python interfaces and Python packages (via MakeSwigLib and MakePythonWheel modules). In this way, the Python-related part of the build mechanism is enclosed in MakePythonAPI.

• Differentiated between BORNAGAIN_PYTHON variable and WITH_PYTHON_API argument:

  • BORNAGAIN_PYTHON = Add Python-related functionality to the C++ libraries.
  • WITH_PYTHON_API = Add a Python interface to the C++ libraries; currently made with SWIG.

• Adapted CMakeLists.txt for all modules (Base, Fit, etc.) to the new interface of MakeSharedLib.

• GUI:

  • SampleListView: Added proper preprocessor guards for BORNAGAIN_PYTHON.
  • Improved and cleaned up CMakeLists.txt.
  • Test: Minor improvements.