update README
Merge branch 'develop' into release-13.02
Merge branch 'release-13.02' of https://github.com/chocoteam/Choco3 into release-13.02
Fix few things about real variables (eg. solution backup and solver association)
Debug Count 1
Fix Count (unstable), modify ICause (remove unused methods), refactor IView and IVariableMonitor to forget the cause.
Partial fix of GCC
Add getters in Constraint
Before refactoring prop. engine, few little things
Update fzn builder to handle annotation anew
Move event masks into Propagator:

- update propagation engines,
- remove PropagationStrategies, ArcEngine,
- fix initial propagation in DSLEngine
Update fzn builder to handle annotation anew
Fix variables declaration for unaries, binaries and ternaries
re-plug the explainer
change EqView and BoolEqView
Add count constraint
Add 2 additional parameters in configuration.properties

- add MUL_OCC_VAR_PROP to react on multiple occurrences of a variable in a propagator
- add IDEMPOTENCY to detect non idempotency - FakeEngine.
- add #duplicate() method for variable (not yet implemented for SetVar and GraphVar),
Add comments in Propagator, change IBitset by BitSet in propagation engine, set default values in configuration.properties
First run over propagators to check variables declaration!!
set solution