Allow piece promotion by pieceToChar in all variants

Allow piece promotion by pieceToChar in all variants

If the pieceToCharTable specifies a piece has a promoted version,
by defining the latter as '+', this will now trigger the promotion
procedure when such a piece moves to touch the zone. Legality testing
will consider such moves legal. The promotion character will be a '+',
in SAN generated as an '=+' suffix (to not confuse with check), while
deferral will have no suffix. Pieces without specified promoted version
do not promote, unless they are Pawns. These then offer choice between
all pieces, as usual.