Refactored the rendering sequence so that different renderers (spritebatch, shaperenderer...) are managed by the render method in the main class, but delegate further drawing to all objects in the list. A draw call receives a render method as argument, and calls a specific draw method in the DefaultSprite class. drawShape() or drawBatch(). These can be inherited by subclasses at will.

For this, the powerup library had to be modified. BatchManager is now in charge of maintaining all the renderers. Will need to think about what else it will manage.