Add process_components_cif script to back refactoring branch in stub form

The script process_components_cif was the major product of the initial ccd_utils project milestone #1 %Improve PDBe Chemical Components backend infrastructure using RDKit: beta test version that was completed in September 2017.

Project milestone #3 %refactor ccd_utils with better class structure. is to completely replace the code in the initial project but process_components_cif` is a well considered script that achieved its aims:

Script for PDBeChem backend infrastructure.
Processes the wwPDB Chemical Components Dictionary file components.cif
producing files for

http://ftp.ebi.ac.uk/pub/databases/msd/pdbechem/

To do this components.cif is split into individual PDB chemical component
definitions cif files, sdf files, pdb files and image files.
In addition creates chem_comp.xml and chem_comp.list for all components.

The unit tests test_process_components_cif_cli.py are worth updating and preserving