Primitive Smelter polishments

[MCTian-mi]

This PR:

• makes Primitive Smelter to have non-strict bus placement requirement (i.e. import/export buses can now be put anywhere rather than specific layers).
• makes that Primitive Buses have 4 slots, but each slot now can only hold 16 items in it. So players don't need to put too many buses on a primitive smelter if they just want to operate it manually.
• limit minimum casing counts instead of buses.

This have been tested in a dev environment.

[MCTian-mi]

This might need some discussion idk

[bruberu]

Excellent! Especially with the snow predicate. Well, and I suppose it probably doesn't hurt too much to loosen the hatch requirements a little...