Fix search log when using skills

In case of we pick a sub-optimal move be
sure to print this, and not the best one
on seach log file.

Bug spotted by Guenther Demetz.

No functional change.
Fix a typo

No functional change.
Fix incorrect 'ss' pointer in early stop check

The exclusion search used to verify one move is much
better than other shall be called with 'ss' and not
'ss+1'

No functional change.
Introduce Cut/All node definitions

Follow Don Dailey definition of cut/all node:

"If the previous node was a cut node, we consider this an ALL node.
The only exception is for PV nodes which are a special case of ALL nodes.
In the PVS framework, the first zero width window searched from a PV
node is by our definition a CUT node and if you have to do a re-search
then it is suddenly promoted to a PV nodes (as per PVS search) and only
then can the cut and all nodes swap positions. In other words, these
internal search failures can force the status of every node in the subtree
to swap if it propagates back to the last PV nodes."

http://talkchess.com/forum/viewtopic.php?topic_view=threads&p=519741&t=47577

With this definition we have an hit rate higher than 90% on:

    if (!PvNode && depth > 4 * ONE_PLY)
        dbg_hit_on_c(cutNode, (bestValue >= beta));

And an hit rate of just 28% on:

    if (!PvNode && depth > 4 * ONE_PLY)
        dbg_hit_on_c(!cutNode, (bestValue >= beta));

No functional change.
Use alpha instead of beta-1

It is more directly related to a fail-low.

No functional change.
Retire psq_delta()

No functional change.
Introduce operator~(Piece c)

Small syntactic sugar to reverse piece color.

No functional change.
More consistent 'piece' variable naming

No functional change.
Convert pieceSquareTable to 3 dimensions

No functional change.
Zobrist::init() should be Position::init()

No functional change.
Merge branch 'cut_all' of https://github.com/mcostalba/Stockfish