rearrange bits in bond invars

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2445 a5045d30-4826-4484-9c7f-6e55a06ddc77
fix and test github issue 12

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2446 a5045d30-4826-4484-9c7f-6e55a06ddc77
change bond hash for the original algorithm;
add optional (compile time) collision reporting

git-svn-id: svn://svn.code.sf.net/p/rdkit/code/trunk@2447 a5045d30-4826-4484-9c7f-6e55a06ddc77