Added treasure!

The update no-one asked for, scoring and treasure!

I initially didn't add treasure because I thought it would slow the game down too much, but seeing the waves of ammo in certain rooms, my fears weren't justified. So that's back, along with score for treasure, killing enemies, and changing level. You get an extra life every 40000 score. I also added the extra life orb.

Some other minor changes, such as I/K as forward/backward options, some more SuperCPU fixes, stopping dogs from opening doors (our dog can do this but fortunately Nazi dogs can't), and a bug fix that could prevent you from opening doors if there were too many corpses keeping other doors open.

I also open sourced the game at https://github.com/Kweepa/Wolf64.