Implemented Image actor.

Implemented an image actor, which can render images as 2D elements on top of the scene. This can be used to display logos for Batch images. Closes #416 (closed)

The actor is implemented using actor components. That means, the sprite logic itself is inside an actor component, which is now also used by the light actor. That way, sprite / image rendering is modularized. The sprite component can render world space and pixel / clip space sprites. The world space sprites are always aligned with the camera and always stay the same size.

Clip Space sprites always have an anchor, where they always stay relative to. The pixel space position of the sprite is also always relative to the anchor.

The image actor uses that component to display the image in clip space. The actor itself implements dragging, so that the image can be interactively repositioned.