adding the new item Battery by modifying MetalJunk
new file:   assets/textures/battery.png
deleted:    assets/textures/metalJunk.png
modified:   src/game/GameLoop.java
renamed:    src/item/MetalJunk.java -> src/item/Battery.java
modified:   src/rendering/TextureManager.java
fixing bugs due to a quick commit

modified:   src/game/GameLoop.java
modified:   src/rendering/TextureManager.java