Change Detection in importOldDatabase.py script

This change-detection seems to be working now.
Not implemented for statmech.groups or forbiddenStructures, but you can do so if we have them.

It looks to me like the database needs quite a bit of cleaning up before an import/export is a null change.
Also, before doing a full import, you may want to change the default units on imported kinetics entries (perhaps cm and kcal, as that's what we're importing).
And check we don't introduce rounding errors or other accidental changes.
Have fun!