Potential improvements to Automatic Texture Loading

[danielfeather]

Currently the system that is responsible for texture loading isn't that that flexible, it won't update the Handle<Image> if the Handle<SpriteSheet<T>> changes on the entity and texture loading is on.

I am not sure if its a good idea to replace the texture in this circumstance, it might be better and more efficient to instrct the developer to remove the Handle<Image> if they are changing the Handle<SpriteSheet<T>> on the entity, then the absense of a Handle<Image> could trigger the loading functionality.