Set default option partCoreEdge='core' in saveOutputFile function to not break old code.
Return a proper Chemkin species identifier even if it exceeds 15 characters.

15+ character species identifiers work fine in later versions of CHEMKIN.
It might break CHEMKIN 2.0 though, but let's just print a warning for it.
Write a useful error message when you cannot save a species to the dictionary when writing chemkin file.