global:
-------
- put some documentation in .mli files
- try some more heuristics to extract models for simplexes over ints.
- add the ability to do some encoding (with a flag): (eg. cubes-test
for LIA)
- add optimization capabilities


assertBounds.ml:
----------------

- assert_var and assert_poly should ignore bounds when Pb is UNSAT

- assert_var and assert_poly should ignore bounds that are implied by
  those of the simplex

- add a mode for assert_var and assert_poly to ignore previously
  asserted bounds ? (i.e. mode force_bounds) useful for assertUI.ml ?

- deduce bounds from the simplex ?
