Rebalance Big Mining Drill quality to scale "Ore longevity" smoothly

[rburny]

Big Mining Drill resource drain scales with quality in a linear fashion, reducing drain by ~8% per level & 17% for legendary. This looks natural until you realize that what matters more is actually the inverse of this number, which effectively defines "ore patch longevity". And this number scales pretty wildly:

* normal: 2x (baseline)
* uncommon: 2.44x (1.22x improvement)
* rare: 3x (1.5x improvement)
* epic: 4x (2x improvement)
* legendary: 12.5x (6.25x improvement, over 3x better than epic!)

In particular, the gap between epic & legendary is so large that it barely makes sense to use uncommon-epic BMDs. I would suggest to rebalance the quality tiers such that the progression is more gradual, making even an uncommon/rare BMDs a satisfying upgrade. Here are two potential options:

1. More aggressive: linear 2x-6x scaling (like science bottles):

* normal: 50% drain
* uncommon: 25% drain (2x longevity improvement)
* rare: 17% drain (3x improvement)
* epic: 12.5% drain (4x improvement)
* legendary: 8% drain (~6x improvement)

2. Less aggressive: scale with the square of the usual scaling factor (1.3 / 1.6 /1.9 / 2.5 squared)

* normal: 50%
* uncommon: 30% (~1.69x improvement)
* rare: 20% (~2.56x improvement)
* epic: 14% (~3.61x improvement)
* legendary: 8% (~6.25x improvement)

[AileTheAlien]

Seems good to me!