Python script to generate torsion definition files

A python script should be made that reads a molecule from an SDF file using RDKit, then extracts the non-redundant torsion angles and writes their atom numbers to a file as described in issue #1303. With non-redundant it is meant that if the final group is a terminal group, such as a X-CH3 or X-NH2, only one torsion needs to be defined around the X-C, respectively X-N bond.