python state class now uses CoolPropStateClassSI directly rather than passing through PureFluidClass (10% faster).  Ideally we could make State class that derives from StateSI class just like in C++.  That would make things even faster because it would avoid the unit conversion issues.

Also regenerated constants modules using the script in dev/scripts/generate_constants_module.py which had to be rewritten due to changes in GlobalConstants.h

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>