Use Python Fabio library to load images

PyCore module is extended to use Python Fabio library to load detector images of various formats. A class NumpyArrayWrapper is implemented to wrap a Numpy array (in PyCore/Embed/PyObjectPtr) which is the output of the fabio.open function. The headers of image files are also converted into a std::map to be accessed from C++ side.

Corresponding tests are added to Tests/Unit/PyBinding/EmbeddedTest and the required test data is added to testdata/fabio. The test data are obtained from https://doi.org/10.5281/zenodo.2546760.

The next step is to build the corresponding widgets in the GUI.