Add support for USI protocol

Add support for USI protocol

Specification: http://hgm.nubati.net/usi.html

- Switch protocol when receiving uci/usi command,
  or when option "Protocol" is changed.
- Support parsing of SFEN, but internally use FEN.
- Use shogi coordinates (e.g., 3e3d) for all moves,
  and notation with "*" for piece drops.
- Specify mate distance in ply instead of fullmoves.
- Todo: Adapt option names to be compliant with USI
  - No whitespaces.
  - Standard options should be prefixed by "USI_".