Simplify Outposts #2176

Simplify Outposts #2176

This is a functional simplification. This is NOT the exact version that was tested. Beyond the testing, an assignment was removed and a piece changes for consistency.

Instead of rewarding ANY square past an opponent pawn as an "outpost," only use squares that are protected by our pawn. I believe this is more consistent with what the chess world calls an "outpost."

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 23540 W: 5387 L: 5269 D: 12884
http://tests.stockfishchess.org/tests/view/5cf51e6d0ebc5925cf08b823

LTC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 53085 W: 9271 L: 9204 D: 34610
http://tests.stockfishchess.org/tests/view/5cf5279e0ebc5925cf08b992

bench 3424592