PyCrysFML documentation

PyCrysFML has started to be documented with sphinx. Documentation is stores in docs/pycrysfml. The documentation in html format is accesible from https://pycrysfml.readthedocs.io/en/latest/index.html.

The module CFML_Scattering_Tables has been completely documented. The documentation describes in detail tables, dictionaries and functions. Every function has its own example.

New functions have been added to the Fortran module CFML_Scattering_Tables to make tables directly accesible from Python. These functions are able to extract rows from these tables. This rows are returned to Python in the form of a dictionary.