Allow LuaEntity.graphics_variation to be blueprintable

[Earendel]

Please allow the graphics_variation property of supporting entities (e.g: simple-entity-with-force) to be saved to a blueprint. When the ghost entities are made from the blue print, please can the ghosts also be given the correct graphics_variation, and for that to be carried through to the revived entity too.

Use case: Text Plates: A single item places a metal plate in the shape of a letter or symbol. A script sets a specific graphics_variation so that a line of these entities can make a word. The word gets blueprinted and then placed elsewhere, so the blueprint needs to store, display, and place the correct graphics variations.

Thanks.