Added features and bug fixes

+Added weapon tiers that are unlocked as the waves progress
+Re-added Chem Zombie with reduced damage
+Fixed PointSave function showing -- when going into negative numbers
+Removed derma modification as it tampers with ULX and HatsChat2
+Lifted point save limit as weapons are now unlocked in tiers (no
Boomstick on Wave 1 or 2)