Alpha 1.3 Christmas Update

Alpha 1.3 Christmas Update

Features:

- Reduced duration of gun's recoil animation;
- Added new barricades (currently non-functional, zombies can get through):
    - Sandbag;
    - Wooden barricade;
    - Metal barricade;
    - Barbed wire;
- Added Enemy Inventory, now zombies can carry items and drop them;
- Added a new UI image for when the player points at an item they can pick up (currently only a square);
- Fixed missing Spawner in game's map;
- Added Christmas;