Allow game entity to reference arbitrary data in render updates

[heinezen]

In our engine architecture, game entities in the simulation send requests to the renderer to be drawn. The render requests also include updates on what to draw (i.e. which animation) and where (i.e. the entity position). Updates are only send when this info changes.

Currently, we only send information in updates that is always required by the renderer, e.g. the animation path and the entity position. However, we may want to send other information that is only used in specific cases such as the player ID when drawing player colors. Furthermore, the renderer also needs to be able to handle this info and transform it into something that can be passed to the GPU.

Tasks:

• Game simulation needs to be able to lookup which data can be send to the renderer (and in which situations)
• Renderer can transform optional data into something usable