Container-prototype: allow SpriteVariations

[tiriscef]

Hey,

I would like to request to let the Container-Prototype use SpriteVariations, similar to the SimpleEntity-prototype.

My usecase: I have a container entity where I expect the player to place a larger amount of and that would look weird when every instance looks identical. So I would like to use more than one sprite.
(In this case I don't use the entity as a chest, but rather as a building and it's inventory as an interface for a scripted behaviour.)

This effect is also kind of visible in vanilla gameplay, where chests are often placed next to each other at train stations or belt buffers:

[Rseding91]

Unless the base game decides to use graphics variations for containers this isn't going to happen. Making an entity support sprite variations means it needs to store the variation runtime + save/load it. That would add extra memory for every container entity runtime and increase save file sizes for every base game save file just for modding support of showing different pictures in chests.

That's not acceptable to me.

[tiriscef]

Making an entity support sprite variations means it needs to store the variation runtime + save/load it.

Even if the entity has just a Sprite defined instead of a SpriteVariation? o.o