Fix disambiguation for one-click moving

Fix disambiguation for one-click moving

The test in the DisambiguateCallback to ignore duplicate moves (as
sometimes generated by Betza descriptions) was only testing for the
same from square. This is good enugh if the to-square is always given
(as in SAN), so that moves with different to-square would always be
rejected anyway. But to determine if a piece has only a single move
we disambiguate with unknown to-square. So all moves but the first
of a piece would be ignored, making it always pass the only-move test.
We now test both from- and to-square, and only ignore moves that
have both of these equal to that of an already matching move.