"Too Easy" mode, and an AI fix

Added "Too Easy" difficulty, which makes your cleaver AoE, gives you 3 times as much health, shortens the level to half as long, gives you 7 lives in top down mode and 13 times as much starting ammo. And the quicktime events won't fail if you press the wrong button.

Too easy you say? Well it's for those times you get stuck somewhere, and you're not having fun anymore.

Also updated zombie AI in topdown levels, to make them avoid walls better. Originally I had the zombies walk to the last location they saw you, and if they didn't see you they would just keep going in that direction until they were stopped by a wall. Based on a lifetime of studying zombies, that's what I knew they would do. But they were ending up in corners, or half inside of walls and shelves, and they were really hard to see. So their new AI has them going to the last location they saw you,and if you're out of sight they won't keep going!! They'll stop right there, move up to 3 feet in a random direction, then turn around so they'll see you more easily when you come back that way.