adding an enum representing every existing item

new file:   src/item/ItemListEnum.java
first version of the inventory handling
only the primary weapon is handled

modified:   src/entity/player/Player.java
modified:   src/game/Game.java
modified:   src/game/GameLoop.java
modified:   src/item/Battery.java
modified:   src/item/Equipment.java
modified:   src/item/Item.java
modified:   src/item/accessory/Accessory.java
modified:   src/item/motionGear/MotionGear.java
modified:   src/item/shield/Shield.java
modified:   src/item/weapon/LaserRifle.java
modified:   src/item/weapon/PrimaryWeapon.java
modified:   src/item/weapon/SecondaryWeapon.java
modified:   src/item/weapon/Weapon.java
new file:   src/userInterface/HUD.java
new file:   src/userInterface/UIController.java
modified:   src/userInterface/inventory/Inventory.java