#147 mmCIF lacks support for chemical components

[Noel O'Boyle]

The PDB provides information on small molecules as chemical components in the mmCIF format (see http://mmcif.rcsb.org/mmcif-early/workshop/mmCIF-tutorials/intro/comp.htm). However, these do not appear to be read by OpenBabel. When the chemical components mmCIF is downloaded from http://www.wwpdb.org/ccd.html, no molecule is read in.