History code rewrite (#1122)

Rearrange and rename all history heuristic code. Naming
is now based on chessprogramming.wikispaces.com conventions
and the relations among the various heuristics are now more
clear and consistent.

No functional change.

src/types.h

@@ -421,6 +421,10 @@ inline Square to_sq(Move m) {
   return Square(m & 0x3F);
 }
 
+inline int from_to(Move m) {
+ return m & 0xFFF;
+}
+
 inline MoveType type_of(Move m) {
   return MoveType(m & (3 << 14));
 }