adding the MetalJunk item

new file:   assets/textures/metalJunk.png
new file:   src/item/MetalJunk.java
modified:   src/rendering/TextureManager.java
Merge branch 'master' into items
adding a new item plus some refactoring

modified:   src/game/GameLoop.java
renamed:    src/item/weapon/LaserRifle.java -> src/item/Item.java
modified:   src/item/MetalJunk.java
modified:   src/item/weapon/LaserRifle.java