Add Glucose 21 dynamic restart strategy and enable it by default
The new Dynamic restart strategy of Glucose 2.1 has been presented in "Refining restarts strategies for SAT and UNSAT formulae. Gilles Audemard and Laurent Simon, in proceedings of CP'2012".
That dynamic restart strategy is going to be Sat4j default instead of Armin Biere's In/Out rapid Restart strategy.