ENH: Make testing of docstrings dynamic
ENH: Make testing of docstrings dynamic

Use dynamic finding and loading of feature classes in `featureextractor.py` to dynamically test the docstrings. Additionally tests the docstring of the class.

Radiomics/pyradiomics,Radiomics/pyradiomics,Radiomics/pyradiomics,Radiomics/pyradiomics