Recognition of projection based stereochemistry.

Some old code left over from June (prev branch: https://github.com/johnmay/cdk/tree/feature/projected-stereochemistry). Not perfect but alright, need do some false positive analysis, chairs are particularly troublesome.

![Stereo](https://lh6.googleusercontent.com/-VBTWHL6qEeY/VJXfFRdlPOI/AAAAAAAAAgo/OyI7mf9DoXg/w625-h408-no/stereo.png)