PDBeChem ftp Output: Supply divided directory

• From issue #13 (closed)
• Currently it is difficult to navigate the ftp site because it takes around 40 seconds to see http://ftp.ebi.ac.uk/pub/databases/msd/pdbechem/images/large/ as it contains 24936 files.
• Instead provide a divided directory with all the files for an individual chemical component.
• so for ATP directory divided/A/ATP would contain:

divided/A/ATP/ATP.cif 
divided/A/ATP/coordinates/ideal/ATP.sdf
divided/A/ATP/coordinates/ideal/ATP.pdb
divided/A/ATP/coordinates/ideal/ATP_no_hydrogen.sdf
divided/A/ATP/coordinates/ideal/ATP.xml
divided/A/ATP/coordinates/model/ATP.sdf
divided/A/ATP/coordinates/model/ATP.pdb
divided/A/ATP/coordinates/model/ATP_no_hydrogen.sdf
divided/A/ATP/2Dimages/with_labels/ATP.xml
divided/A/ATP/2Dimages/with_labels/ATP.png
divided/A/ATP/2Dimages/without_labels/ATP.xml
divided/A/ATP/2Dimages/without_labels/ATP.png

• this will enable users to quickly find what they want (hopefully?)