Add matfaust.factparams.ConstraintList in the same idea than previous commit did for pyfaust.

Example of what it changes:
Previously: fact_cons = {ConstraintInt('splin', 500, 32, 5), ConstraintInt('sp', 32, 32, 96), ConstraintInt('sp', 32, 32, 96)};
Now: fact_cons = ConstraintList('splin', 5, 500, 32, 'sp', 96, 32, 32, 'sp', 96, 32, 32);

The former expression is still valid, the new one is a shorthand.