TODO new MDD parser:

- error no int, error no real (see Livevalprov)

- document the classes and the grammars
- document the parsing process in a readme file in the package or so

- validation rules:
    - adapt mak-tools for new validation rules, function syntax, multi-unique keys (mdd viewer)
    
- http://bugs.best.eu.org/cgi-bin/bugzilla/show_bug.cgi?id=1098

OPTIMIZATION:
- use caching for creation of virtual fields (from definitions), to avoid parsing twice the same def ?