Fixes

1. Don't reuse seeds improperly in slave generation. Should fix #5635 (closed).
2. Make the Main Menu's sanity checking run isSlave on all the slaves in the slave array and report failures. I've seen way too many examples recently of saves that have bizarre failures because the slaves fail an isSlave check; hopefully earlier reporting will help.
3. Improve the robustness of isDevelopmentFacilityLeader. It really shouldn't ever be passed null but it's well-defined and consistent to say that the null slave is NOT a development facility leader.
4. Fix some type stuff.