V1.1 bug fixes and tweaks

Fixed some bugs to make the AI less buggy (though still far from perfect), and tweaked the gameplay to be more balanced.

Some additional info  in version 1.1: 

- Cops can get killed by friendly fire, and they always drop a health pack when they do. 

- Each health pack now heals 5 health points (previously only 1)

- Some health packs are now randomly spawned on the map at the start of the game.

- Bullet speeds are now slower, but still quite challenging.