Tweak piece values for drop variants

Tweak piece values for drop variants

as well as for racing kings.

crazyhouse STC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 4655 W: 2339 L: 2172 D: 144
http://www.variantfishtest.org:6543/tests/view/5ddaff406e23db1ffe4a27c1

crazyhouse LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 3075 W: 1550 L: 1407 D: 118
http://www.variantfishtest.org:6543/tests/view/5ddb15636e23db1ffe4a27c8

racingkings STC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 3311 W: 1177 L: 1057 D: 1077
http://www.variantfishtest.org:6543/tests/view/5ddaff586e23db1ffe4a27c4

racingkings LTC
LLR: 2.96 (-2.94,2.94) [-10.00,5.00]
Total: 824 W: 284 L: 239 D: 301
http://www.variantfishtest.org:6543/tests/view/5ddba21c6e23db1ffe4a27d4