Eli Mina Overhaul

Overhauled the Eli Mina-related classes:

-	Packing orders into multiple boxes is now supported, meaning that higher quantities may be ordered
-	The algorithm used to pack items into boxes is more flexible (and perhaps more accurate)
-	Arbitrary discounts may be applied (currently quantity-based discounts are applied)

Moreover, many classes have been removed and added, leading to overall better structure.