[ENHANCEMENT] Update MDANSE so that it checks the validity of the cache

**Is your feature request related to a problem? Please describe.**
In many cases the user may have old or corrupted cache. When the user json files are loaded up we should check that the data inside them is correct. For example, that the default atom data has not been changed and the default units are correct.

Probably the best thing to do is to warn the user and attempt a fix to their files.