[Fix #163] Constraint.isSatisfied() should not assume the constraint has been propagated once
[Fix #152] correct constraints dynamic addition

- rename Solver#postCut() in Solver#post() and Solver#post() in Solver#postTemp()
- create unpost method in Solver
- correct AbstractVariable#unlink()
- add IPropagationEngine#dynamicDeletion
- PropagationTrigger now manages 3 types of constraints: ones posted before resolution began, ones posted permanently after resolution began and ones posted temporary after resolution began.

and remove LightVariableEngine (useless)
Merge branch 'feature-dyna' into develop