Find cyclic and polycyclic vertices in graphs.

Also added aromaticity test for molecules.
Import polycyclic thermo groups from RMG-Java.
Search for polycylic ring strain correction prior to individual ring corrections.

Assumes a single polycyclic ring strain correction per molecule.  Gives error when
correction cannot be found.
Turned on cyclic symmetry numbers and updated algorithm.

The old algorithm needed some updates to reflect earlier refactoring and to
give reasonable estimates of the cyclic symmetry number. Also added some
unit tests for a few cyclic molecules.
Merge branch 'polycyclic'