refined substructure extraction logic; optimized atom filtering, bond…

… copying, and hydrogen recalculation handling

reactor now handles extended stereo

added skip_elements support for metal handling functions; introduced …

…bond rescaling helper.

added iupac alias to opsin

added fixes for some heterocycles.

fixed cache invalidation in tautomers standardization.

bump

sticky smiles api update

C SP3 fraction fix

SSSR cython (#59)

SSSR reimplemented on cython with x10-100 speedup depends on mol size