post-academic

After a little academic discution, I decided to aim on some working examples with what I have more than on new implementation for now.
As the language is basically declarative, I came to implement in NUL (and try to resolve with NUL) the Zebra puzzle.

As a result, the object's attribute and OO implementation didn't move at all, what was lately done, though, was :
- A lot of TODO about optimisation and detail fixing have been done and are not to do anymore
- The 'solving engine' embryo is created.

This 'solving engine' is the process needed at the end of the zebra puzzle, to get one answer out of an expression, described here.