perhaps some inefficiency since there are more propagators

 - RealValue: constants
 - Dom_interval: interval domaine
 - Dom_polynome: Polynome, pivot (shostak theory like)

        Since types are more fluid in colibri2 adding a type to a congruence
        class can create possible matches

  Don't use Expr.* for ground terms and type

   except the one about efficiency with learning

    Forgotten substitution of the arguments

 Modifications made by François Bobot, Stéphane Graham-Lengrand and Guillaume
 Bury. The witan licence has been used for the files not mainly modified by Bobot

Bit vectors: propagation and simple tests

The propagation for the logic operators' subset of bv is done. Adding two files, no serious change to other files.

See merge request !3