Add sphere appearance data

[jakubg1]

Add a sphere appearance data structure, which would define a sphere entity's appearance. For example:

• Main sprite,
• Overlays, such as reflections,
• Optional overlays, such as chains,
• Particles for sphere effects,
• Sphere destroy particles,
• More animations for spheres like the scarab - for moving forwards, backwards in set loops plus slow/stop/reverse animations...