Some set propagators do not accept ISetDeltaMonitors that are not of the type SetDeltaMonitor.

For example, the following code will throw an ArrayStoreException:

	Solver solver = new Solver();
	SetVar v1 = VF.fixed("{0,1}", new int[]{0, 1}, solver);
	SetVar v2 = VF.set("v2", 0, 3, solver);
	solver.post(SCF.subsetEq(new SetVar[]{v1, v2}));
	solver.set(SetStrategyFactory.force_first(new SetVar[]{v1, v2}));
	if (solver.findSolution()) {
		do {
			System.out.println(v1 + " subseteq " + v2);
		} while (solver.nextSolution());
	}
Merge pull request #182 from JLiangWaterloo/develop

Some set propagators do not accept ISetDeltaMonitors that are not of the...