Add several options to CAR

* spot/twa/acc.hh: Remove useless comment.
* spot/twaalgos/car.cc: Rewrite the implementation to try
  multiple algorithms and choose the best, add the possibility
  to force the order of the colors/pairs in LAR and use
  propagate_marks_here.
* spot/twaalgos/car.hh, tests/python/car.py: Create a new system of
  options for CAR.
* spot/twaalgos/degen.cc, spot/twaalgos/degen.hh: Add the possibility
  to forbid some marks in is_partially_degeneralizable.

spot/twa/acc.hh

@@ -592,7 +592,6 @@ namespace spot
         }
         if (elements.size() == 2)
         {
-          // Vaut 1 si si c'est le 2e qui est bon
           unsigned pos = elements[1].back().sub.op == op
                         && elements[1][0].mark.count() == 1;
           if (!(elements[0].back().sub.op == op || pos))