CIF/BDD: The saturation exploration strategy should provide debug information

Currently saturation prints no debug information. So when some reachability computation takes a long time, it's now difficult to see why it's taking long or on what part it hangs. Note that there is a corresponding JavaBDD issue (https://github.com/com-github-javabdd/com.github.javabdd/issues/66) to adapt saturation on the side of JavaBDD. Once completed, CifBddReachability must be updated to make use of the added debug functionality, which will (probably) be a callback mechanism.