Merge remote-tracking branch 'origin/master'

src/main/java/engine/Kernel.java

src/main/java/engine/Sound.java

src/main/java/engine/graphic/GraphicEngine.java

src/main/java/engine/graphic/ImageComponent.java

src/main/java/engine/graphic/RectangleComponent.java

src/main/java/engine/physic/Movable.java

src/main/java/engine/physic/PhysicEngine.java

src/main/java/pong/PongApp.java

src/main/resources/pong/ball.png