Merge pull request #21 from mcostalba/master

Tweak bishop pair and knight weight
Merge pull request #24 from mcostalba/master

Use a formula for chain membership bonus
Merge branch 'master' of https://github.com/mcostalba/Stockfish
Merge branch 'master' of https://github.com/mcostalba/Stockfish
Merge branch 'master' of https://github.com/mcostalba/Stockfish
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'origin/master' into syzygy1
Merge remote-tracking branch 'upstream/master'
Revert previous patch

It seems a regression at 15+0.05:
ELO: -4.82 +-2.1 (95%) LOS: 0.0%
Total: 40000 W: 7181 L: 7736 D: 25083

bench: 8331357
Merge remote-tracking branch 'upstream/master' into syzygy1
Merge remote-tracking branch 'syz/master' into syzygy1