Minor update

Some drugs now have a separate card for selling when Working the streets.
Their slots are now taken up with other things.
You can now bundle and sell heroin.
You can now bundles and sell Anabolic steroids.
Adjusted the thresholds for Overtraining?

Another attempt at fixing a bug preventing playing some characters that haven't been played in a while
Fixed the final exam on Covedale/Mechanics and engineering not working properly.
Fixed some more typos; thanks for the reports!