Store moves sent with "position" UCI command

Store all the game moves until current position.

This will be used by next patch.

No functional change.
Fix easy re-capture case

We detect an easy move as a recapture with an
high margin on the second best move.

Unfortunatly the recapture detection is broken
becuase we identify as a recapture any move that
follows an opponent's previous capture !

This patch fix the logic to correctly detect a
real re-capture.

No functional change.
More easy move tweaks