0.3.0 Initial zombie design complete

In this update many features have been added and bugs have been fixed. Here's the list of what I have worked on:

1. Weapon-melee systems polishing:
   1. Camera shake when reloading.
   2. Camera shake for melee attack.
   3. Fire mode selection (for the assault rifle - you can now choose between automatic or semiautomatic fire).
   4. Melee attack visual and sound effects.
   5. More melee system debugging.
2. Zombie design:
   1. Animation consistency debugging.
   2. Sound effects design.
   3. Sound event managing: when sounds like shooting, explosions, reloading, walking are emitted, zombies will sense the sounds if they are in the hearing range. Every sound event has a loudness variable, so for example footsteps will be less likely to be heard than reloading or louder events.
   4. Bloodsplash sound when hitting zombies. This is a small addition to the sound design of the game, but I think it helps to make the shooting feeling more pleasant.
   5. Zombie can now be hit by exploding barrels. This feature is modular and can be easily added to all sorts of explosions in the future.
   6. Zombie AI debugging.