[Fix #177 - Fix #179]
[Fix #177 - Fix #179]

- add a ContradictionException to NoPropagatioEngine to handle with empty domain variables

Tiger66639/choco3,chocoteam/choco3,cp-profiler/choco3,PhilAndrew/choco3gwt,cp-profiler/choco3,piyushsh/choco3,chocoteam/choco3,piyushsh/choco3,piyushsh/choco3,cp-profiler/choco3,Tiger66639/choco3,Tiger66639/choco3,PhilAndrew/choco3gwt,cp-profiler/choco3,piyushsh/choco3,chocoteam/choco3,chocoteam/choco3,PhilAndrew/choco3gwt,Tiger66639/choco3