Dynamic complexity

Dynamic complexity

Instead of computing the initiative bonus on the material score + dynamic score
compute it on (material score/2) + dynamic score,

Passed STC
http://tests.stockfishchess.org/tests/view/5e2c4945ab2d69d58394fa8f
LLR: 2.94 (-2.94,2.94) {-1.00,3.00}
Total: 39387 W: 7594 L: 7386 D: 24407
Ptnml(0-2): 658, 4519, 9165, 4649, 697

Passed LTC
http://tests.stockfishchess.org/tests/view/5e2c85ccab2d69d58394faa7
LLR: 2.95 (-2.94,2.94) {0.00,2.00}
Total: 32588 W: 4206 L: 3986 D: 24396
Ptnml(0-2): 244, 2909, 9738, 3111, 253

closes https://github.com/official-stockfish/Stockfish/pull/2516

Bench: 4765486