* add option to use chiral presence in atom ranking
* add findMesoCenters
* add includeChiralPresence to python wrapper
* add python wrapper for that
* backup, not working
* backup
* all tests pass
* add tests for partial coverage of stereo groups
all tests pass
* backout the cleanup operations for the initial merge
* track the meso atoms with atom properties.
this is an optimization for later.
* changes in response to review