Tweak piece values for drop variants

Tweak piece values for drop variants

and variants where check is prohibited.

crazyhouse STC (yellow)
LLR: -2.97 (-2.94,2.94) [0.00,10.00]
Total: 16416 W: 8023 L: 7887 D: 506
http://www.variantfishtest.org:6543/tests/view/5dfe8f2f6e23db1ffe4a28ee

crazyhouse LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 2507 W: 1275 L: 1140 D: 92
http://www.variantfishtest.org:6543/tests/view/5dff13b16e23db1ffe4a28f3

racingkings STC
LLR: 2.98 (-2.94,2.94) [-10.00,5.00]
Total: 4507 W: 1524 L: 1501 D: 1482
http://www.variantfishtest.org:6543/tests/view/5dffdcfe6e23db1ffe4a28fb

racingkings LTC
LLR: 2.97 (-2.94,2.94) [-10.00,5.00]
Total: 1150 W: 362 L: 320 D: 468
http://www.variantfishtest.org:6543/tests/view/5dffdcf26e23db1ffe4a28f9