Improve validations

[innerbytes]

Will put here which validations can be improved

• in gameObject.setSpriteId - good to validate this sprite exists
• In gameObject.setAnimation - also can validate this animation exists, but only if the 3d entity id is already set. Otherwise should not validate and should let user to dangerously set whatever
• The same with gameObject.setBody

... let's see if some more will accumulate.