- fixed a bug in the MMFF stretch-bend gradient calculation
- put in better evidence the extents of the UFF hack so that it can be
  easily commented out if required
Merge pull request #126 from ptosco/master

Critical bug fix in the MMFF stretch-bend gradient calculation
remove USR references from SWIG wrappers
changes suggested by Roger S:
add residueNumber
serialNumber -> int
add segmentNumber
a couple of small vector modifications
add a couple new descriptors
merge branch 'master' of https://github.com/nhfechner/rdkit