add support for including chirality in the AtomPairs and TopologicalTorsions descriptors

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2477 a5045d30-4826-4484-9c7f-6e55a06ddc77
support getting atom contributions to hkAlpha; support chiral flags for torsions and atom pair fingerprints

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2478 a5045d30-4826-4484-9c7f-6e55a06ddc77